Articles de revues : « Aminopeptidase N »

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Jóźwik, Artur, Ewa Polawska, Nina Strzałkowska, Krzysztof Niemczuk, Małgorzata Łysek-Gładysińska, Agnieszka Kamińska et Monika Michalczuk. « Effect of linseed, rapeseed, and vitamin E long term supplementation on the activity of the lysosomal enzymes in ostrich liver ». Bulletin of the Veterinary Institute in Pulawy 57, n^o 4 (1 décembre 2013) : 573–78. http://dx.doi.org/10.2478/bvip-2013-0098.

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Abstract The aim of the study was to assess the activity of lysosomal enzymes: aminopeptidases, including alanine aminopeptidase (AlaAP), leucine aminopeptidase (LeuAP), arginine aminopeptidase (ArgAP), and glycosidases, such as β-galactosidase (BGAL), β-glucuronidase (BGRD), β-glucosidase (BGLU), N-acetyl-β-hexosaminidase (HEX), α-glucosidase (AGLU) and α-mannosidase (MAN) in the liver of ostriches (n = 80) fed diet supplemented with linseed (4% and 8%) and rapeseed (5% and 10%), with low and high level of vitamin E. (40 and 100 mg). The results indicate that higher level of vitamin E or 4% linseed supplementation in ostrich diet generally increase the activity of glycosidase enzymes and decrease the activity of aminopeptidases in the liver. The 8% linseed and rapeseeds feeding in decreased the activity of AlaAP, LeuAP, and ArgAP and increased only the activity of BGLU.

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Varona, Adolfo, Lorena Blanco, José I. López, Javier Gil, Ekaitz Agirregoitia, Jon Irazusta et Gorka Larrinaga. « Altered levels of acid, basic, and neutral peptidase activity and expression in human clear cell renal cell carcinoma ». American Journal of Physiology-Renal Physiology 292, n^o 2 (février 2007) : F780—F788. http://dx.doi.org/10.1152/ajprenal.00148.2006.

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Peptides play important roles in cell regulation and signaling in many tissues and are regulated by peptidases, most of which are highly expressed in the kidney. Several peptide convertases have a function in different tumor stages, and some have been clearly characterized as diagnostic and prognostic markers for solid tumors, including renal cancer; however, little is known about their in vivo role in kidney tumors. The present study compares the activity of a range of peptidases in human tumor samples and nontumor tissue obtained from clear cell renal cell carcinoma (CCRCC) patients. To cover the complete spectrum and subcellular distribution of peptide-converting activity, acid, neutral, basic, and omega activities were selected. CCRCC displays a selective and restricted pattern of peptidase activities. Puromycin-sensitive aminopeptidase activity in the tumor increases [tumor (t) = 10,775 vs. nontumor (n) = 7,635 units of peptidase (UP)/mg protein; P < 0.05], whereas aminopeptidase N decreases (t = 6,664 vs. n = 33,381 UP/mg protein; P < 0.001). Aminopeptidase B activity of the particulate fraction in tumors decreases (t = 2,399 vs. n = 13,536 UP/mg protein; P < 0.001) compared with nontumor tissues, and aspartyl-aminopeptidase activity decreases significantly in CCRCC (t = 137 vs. n = 223 UP/mg protein; P < 0.05). Soluble and particulate pyroglutamyl peptidase I activities, aminopeptidase A activity, and soluble aminopeptidase B activity do not vary in renal cancer. The relative expression for the aforementioned peptidases, assayed using quantitative RT-PCR, increases in CCRCC for aminopeptidases B (1.5-fold) and A (19-fold), aspartyl-aminopeptidase (3.9-fold), puromycin-sensitive aminopeptidase (2.5-fold), and pyroglutamyl peptidase I (7.6-fold). Only aminopeptidase N expression decreases in tumors (1.3-fold). This peptidase activity profile in the neoplastic kidney suggests a specific role for the studied convertases and the possible involvement of an intracrine renin-angiotensin system in the pathogenesis of CCRCC.

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Veillard, Florian, Barbara Potempa, Marcin Poreba, Marcin Drag et Jan Potempa. « Gingipain aminopeptidase activities in Porphyromonas gingivalis ». Biological Chemistry 393, n^o 12 (1 décembre 2012) : 1471–76. http://dx.doi.org/10.1515/hsz-2012-0222.

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Abstract Bestatin, a specific inhibitor of metalloaminopeptidases, inhibits the growth of Porphyromonas gingivalis. To identify its target enzyme, a library of fluorescent substrates was used but no metalloaminopeptidase activity was found. The aminopeptidase activity of P. gingivalis was bestatin-insensitive and directed exclusively toward N-terminal arginine and lysine substrates. Class-specific inhibitors and gingipain-null mutants showed that gingipains were the only enzymes responsible for this activity. The kinetic constants obtained for Rgps were comparable to those of human aminopeptidases but Kgp aminopeptidase activity was weaker. This finding reveals a new role for gingipains as aminopeptidases in the degradation of proteins and peptides in P. gingivalis.

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Matsas, R., S. L. Stephenson, J. Hryszko, A. J. Kenny et A. J. Turner. « The metabolism of neuropeptides. Phase separation of synaptic membrane preparations with Triton X-114 reveals the presence of aminopeptidase N ». Biochemical Journal 231, n^o 2 (15 octobre 1985) : 445–49. http://dx.doi.org/10.1042/bj2310445.

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The property of solutions of Triton X-114 to separate into detergent-rich and detergent-poor phases at 30 degrees C has been exploited to investigate the identities of the aminopeptidases in synaptic membrane preparations from pig striatum. When titrated with an antiserum to aminopeptidase N (EC 3.4.11.2), synaptic membranes solubilized with Triton X-100 revealed that this enzyme apparently comprises no more than 5% of the activity releasing tyrosine from [Leu]enkephalin. When assayed in the presence of puromycin, this proportion increased to 20%. Three integral membrane proteins were fractionated by phase separation in Triton X-114. Aminopeptidase activity, endopeptidase-24.11 and peptidyl dipeptidase A partitioned predominantly into the detergent-rich phase when kidney microvillar membranes were so treated. However, only 5.5% of synaptic membrane aminopeptidase activity partitioned into this phase, although the other peptidases behaved predictably. About half of the aminopeptidase activity in the detergent-rich phase could now be titrated with the antiserum, showing that aminopeptidase N is an integral membrane protein of this preparation. Three aminopeptidase inhibitors were investigated for their ability to discriminate between the different activities revealed by these experiments. Although amastatin was the most potent (IC50 = 5 × 10(−7) M) it failed to discriminate between pure kidney aminopeptidase N, the total activity of solubilized synaptic membranes and that in the Triton X-114-rich phase. Bestatin was slightly more potent for total activity (IC50 = 6.3 × 10(−6) M) than for the other two forms (IC50 = 1.6 × 10(−5) M). Puromycin was a weak inhibitor, but was more selective. The activity of solubilized membranes was more sensitive (IC50 = 1.6 × 10(−5) M) than that of the pure enzyme or the Triton X-114-rich phase (IC50 = 4 × 10(−4) M). We suggest that the puromycin-sensitive aminopeptidase activity that predominates in crude synaptic membrane preparations may be a cytosolic contaminant or peripheral membrane protein rather than an integral membrane component. Aminopeptidase N may contribute to the extracellular metabolism of enkephalin and other susceptible neuropeptides in the brain.

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Galán-Ocaña, A., M. J. Ramírez-Expósito, J. M. Martínez-Martos, S. Tellado et C. Azorit. « Regulation of aminopeptidases by the renin - angiotensin system : monitoring seasonal variations in red deer and fallow deer from a Mediterranean ecosystem ». Animal Production Science 52, n^o 8 (2012) : 761. http://dx.doi.org/10.1071/an12023.

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The circulating renin–angiotensin system (RAS) is well known for its systemic role in the regulation of blood pressure, renal hemodynamics and fluid homeostasis. However, in mammals several organs also contain a local RAS, including male and female reproductive tissues. In the present study we analysed serum from a free-living population of red deer (Cervus elaphus hispanicus) and fallow deer (Dama dama) to determine the activity of four RAS-regulating aminopeptidases (aminopeptidase A, aspartyl aminopeptidase, aminopeptidase N and aminopeptidase B) as part of a study of annual cycles of growth and condition. Our aim was to detect seasonal variations in the activities of these aminopeptidases and their relationship to the reproductive behaviour of both species in a Mediterranean environment. In both males and females there was a maximum peak of activity in autumn. A second peak was detected in spring for males while in females activity was also higher in summer. These changes may be related to a different endocrine status according to their seasonal cycle, the decreased photoperiod in autumn and the normal timing of the seasonal growth cycle. Thus, changes in the activity of RAS-regulating aminopeptidases could reflect the functional role of angiotensins through the annual cycle of both species, also suggesting an important role of these peptide hormones in the regulation of these biological processes.

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Jackson, M. C., Y. Choudry, A. Bourne, J. F. Woodley et A. J. Kenny. « A fluorimetric assay for aminopeptidase W ». Biochemical Journal 253, n^o 1 (1 juillet 1988) : 299–302. http://dx.doi.org/10.1042/bj2530299.

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A novel two-step enzyme-linked assay for aminopeptidase W is described and validated by comparison with other assays. L-alpha-Glutamyl-L-tryptophan (Glu-Trp) is a favoured substrate for this enzyme. With the use of glutamate dehydrogenase (EC 1.4.1.2) in a second step, the assay measured the release of free glutamate from L-alpha-glutamyl-L-tryptophan by the increase in NADH fluorescence. In the presence of 5 mM-1,10-phenanthroline and 50 microM-cilastatin the contribution of other membrane peptidases, in particular aminopeptidases N and A and microsomal dipeptidase in kidney, was very small. Residual cytosolic activities hydrolysing Glu-Trp were sensitive to inhibition by 2.5 mM-N-ethylmaleimide. The activity of aminopeptidase W was unaffected by these inhibitors. There was good correlation between the fluorimetric assay and those in which the free tryptophan released by kidney membrane fractions was determined by h.p.l.c. or the aminopeptidase W was measured immunoradiometrically with a monoclonal antibody.

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Martínez-Martos, José Manuel, María Correa-Rodríguez, Alma Rus, Francisco Molina, María Jesús Ramírez-Expósito et María Encarnación Aguilar-Ferrandiz. « Altered Serum Oxytocinase and Enkephalin-Degrading Aminopeptidase Activities in Patients With Fibromyalgia ». Biological Research For Nursing 21, n^o 4 (26 mai 2019) : 431–39. http://dx.doi.org/10.1177/1099800419854207.

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Objectives: Fibromyalgia (FM) is a chronic pain condition of unclear etiology. We have analyzed, for the first time, the activity of a broad spectrum of aminopeptidases (APs) in patients with FM and controls to investigate whether they are involved in the pathophysiology of this syndrome. Method: In this case–control study, we fluorometrically measured specific AP activities in serum samples of 75 patients with FM and 29 healthy controls. The predictive value of AP activities in FM was determined by receiver operating characteristic (ROC) analysis. Results: Oxytocinase activity was higher in patients with FM than in controls ( p < .001). A subgroup of patients with FM ( n = 18; 24%) showed low levels of enkephalin-degrading aminopeptidase (EDA) activity when compared with the healthy controls ( p < .001) and with the rest of FM patients ( p < .001). There were no significant differences in the activity levels of aminopeptidase A, aminopeptidase B, aspartyl aminopeptidase, insulin-regulated aminopeptidase, pyroglutamyl aminopeptidase, or aminopeptidase N between FM patients and controls. According to ROC analysis, oxytocinase activity may be a good marker for differentiating individuals with FM from healthy subjects. Conclusions: Our findings show that serum oxytocinase activity is increased in patients with FM, which could alter the metabolism of peptides with analgesic effects such as oxytocin and enkephalins. The determination of serum oxytocinase activity may aid in FM diagnosis. Additionally, we have identified a subpopulation of FM patients with abnormally low serum EDA activity.

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ZHANG, Zhen-Zhong, Satoru NIRASAWA, Yoshiaki NAKAJIMA, Michiteru YOSHIDA et Kiyoshi HAYASHI. « Function of the N-terminal propeptide of an aminopeptidase from Vibrio proteolyticus ». Biochemical Journal 350, n^o 3 (8 septembre 2000) : 671–76. http://dx.doi.org/10.1042/bj3500671.

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An aminopeptidase from Vibrio proteolyticus was translated as a preproprotein consisting of four domains: a signal peptide, an N-terminal propeptide, a mature region and a C-terminal propeptide. Protein expression and analysis of the activity results demonstrated that the N-terminal propeptide was essential to the formation of the active enzyme in Escherichia coli. Urea dissolution of inclusion bodies and dialysis indicated that the N-terminal propeptide could facilitate the correct folding of the enzyme in vitro. Using l-Leu-p-nitroanilide as the substrate, the kinetic parameters (kcat and Km) of the pro-aminopeptidase and processed aminopeptidases were analysed. The results suggested that the N-terminal propeptide inhibited enzyme activity of the mature region. In contrast, the C-terminal propeptide did not show evidence of forming an active enzyme, of correctly folding in vitro or of inhibiting the active region.

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Cunningham, Eithne, Marcin Drag, Pawel Kafarski et Angus Bell. « Chemical Target Validation Studies of Aminopeptidase in Malaria Parasites Using α-Aminoalkylphosphonate and Phosphonopeptide Inhibitors ». Antimicrobial Agents and Chemotherapy 52, n^o 9 (5 mai 2008) : 3221–28. http://dx.doi.org/10.1128/aac.01327-07.

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ABSTRACT During its intraerythrocytic phase, the most lethal human malarial parasite, Plasmodium falciparum, digests host cell hemoglobin as a source of some of the amino acids required for its own protein synthesis. A number of parasite endopeptidases (including plasmepsins and falcipains) process the globin into small peptides. These peptides appear to be further digested to free amino acids by aminopeptidases, enzymes that catalyze the sequential cleavage of N-terminal amino acids from peptides. Aminopeptidases are classified into different evolutionary families according to their sequence motifs and preferred substrates. The aminopeptidase inhibitor bestatin can disrupt parasite development, suggesting that this group of enzymes might be a chemotherapeutic target. Two bestatin-susceptible aminopeptidase activities, associated with gene products belonging to the M1 and M17 families, have been described in blood-stage P. falciparum parasites, but it is not known whether one or both are required for parasite development. To establish whether inhibition of the M17 aminopeptidase is sufficient to confer antimalarial activity, we evaluated 35 aminoalkylphosphonate and phosphonopeptide compounds designed to be specific inhibitors of M17 aminopeptidases. The compounds had a range of activities against cultured P. falciparum parasites with 50% inhibitory concentrations down to 14 μM. Some of the compounds were also potent inhibitors of parasite aminopeptidase activity, though it appeared that many were capable of inhibiting the M1 as well as the M17 enzyme. There was a strong correlation between the potencies of the compounds against whole parasites and against the enzyme, suggesting that M17 and/or M1 aminopeptidases may be valid antimalarial drug targets.

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Wanat, Weronika, Michał Talma, Małgorzata Pawełczak et Paweł Kafarski. « Phosphonic Acid Analogues of Phenylglycine as Inhibitors of Aminopeptidases : Comparison of Porcine Aminopeptidase N, Bovine Leucine Aminopeptidase, Tomato Acidic Leucine Aminopeptidase and Aminopeptidase from Barley Seeds ». Pharmaceuticals 12, n^o 3 (17 septembre 2019) : 139. http://dx.doi.org/10.3390/ph12030139.

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The inhibitory activity of 14 racemic phosphonic acid analogs of phenylglycine, substituted in aromatic rings, towards porcine aminopeptidase N (pAPN) and barley seed aminopeptidase was determined experimentally. The obtained patterns of the inhibitory activity against the two enzymes were similar. The obtained data served as a basis for studying the binding modes of these inhibitors by pAPN using molecular modeling. It was found that their aminophosphonate fragments were bound in a highly uniform manner and that the difference in their affinities most likely resulted from the mode of substitution of their phenyl rings. The obtained binding modes towards pAPN were compared, with these predicted for bovine lens leucine aminopeptidase (blLAP) and tomato acidic leucine aminopeptidase (tLAPA). The performed studies indicated that the binding manner of the phenylglycine analogs to biLAP and tLAPA are significantly similar and differ slightly from that predicted for pAPN.

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Jenö, P., J. R. Green et M. J. Lentze. « Specificity studies on enteropeptidase substrates related to the N-terminus of trypsinogen ». Biochemical Journal 241, n^o 3 (1 février 1987) : 721–27. http://dx.doi.org/10.1042/bj2410721.

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The specificity of the synthetic substrate Gly-[L-Asp]4-L-Lys 2-naphthylamide originally developed for the assay of enteropeptidase (EC 3.4.21.9), was investigated with partially purified aminopeptidase. Our results indicate that, not only enteropeptidase, but also the concerted action of the aminopeptidases of the rat small intestine, can rapidly release 2-naphthylamine from the substrate. A previously undescribed, highly active, dipeptidylaminopeptidase, which hydrolyses a Gly-Asp dipeptide from the N-terminus of the substrate, was detected in rat small intestine. The resulting [L-Asp]3-L-Lys 2-naphthylamide fragment is then degraded by a combination of aminopeptidase A and N to yield free 2-naphthylamine. Thus the present substrate cannot be regarded as being specific for enteropeptidase, and its use leads to an over-estimation of enteropeptidase activity in homogenates and extracts of intestinal tissue. In order to prevent this non-specific hydrolysis by aminopeptidases, stereoisomeric substrates with the sequence L-Ala-D-Asp-[L-Asp]3-L-Lys methyl ester, D-Ala-[L-Asp]4-L-Lys methyl ester and L-Ala-[Asp]4-L-Lys methyl ester were synthesized and tested as alternative substrates by their ability to inhibit the enteropeptidase-catalysed activation of trypsinogen.

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Hooper, N. M., J. Hryszko et A. J. Turner. « Purification and characterization of pig kidney aminopeptidase P. A glycosyl-phosphatidylinositol-anchored ectoenzyme ». Biochemical Journal 267, n^o 2 (15 avril 1990) : 509–15. http://dx.doi.org/10.1042/bj2670509.

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Aminopeptidase P (EC 3.4.11.9) was solubilized from pig kidney membranes with bacterial phosphatidylinositol-specific phospholipase C (PI-PLC) and then purified by a combination of anion-exchange and hydrophobic-interaction chromatographies. Contaminating peptidase activities were removed by selective affinity chromatography. The purified enzyme was apparently homogeneous on SDS/PAGE with an Mr of 91,000. Enzymic deglycosylation revealed that aminopeptidase P is a glycoprotein, with up to 25% by weight of the protein being due to the presence of N-linked sugars. The phospholipase-solubilized aminopeptidase P was recognized by an antiserum to the cross-reacting determinant (CRD) characteristic of the glycosyl-phosphatidylinositol anchor. This recognition was abolished by mild acid treatment or deamination with HNO2, indicating that the CRD was due exclusively to the inositol 1,2-cyclic phosphate ring epitope generated by the action of PI-PLC. The activity of aminopeptidase P was inhibited by chelating agents and was stimulated by Mn2+ or Co2+ ions, confirming the metallo-enzyme nature of this peptidase. Selective inhibitors of other aminopeptidases (actinonin, amastatin, bestatin and puromycin) had little or no inhibitory effect.

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Other, Lisa D., et Nigel M. Hooper. « Proteolytic Fragmentation of Aminopeptidase N ». Biochemical Society Transactions 27, n^o 1 (1 février 1999) : A54. http://dx.doi.org/10.1042/bst027a054a.

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Kontoyiannis, Dimitrios P., Renata Pasqualini et Wadih Arap. « Aminopeptidase N inhibitors and SARS ». Lancet 361, n^o 9368 (mai 2003) : 1558. http://dx.doi.org/10.1016/s0140-6736(03)13186-8.

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Danziger, Robert S. « Aminopeptidase N in arterial hypertension ». Heart Failure Reviews 13, n^o 3 (16 novembre 2007) : 293–98. http://dx.doi.org/10.1007/s10741-007-9061-y.

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Anamika Singh, Anamika Singh, et C. V. S. Siva Prasad. « Insilico Comparative Analysis of Functional Residues in Aminopeptidase-N ». International Journal of Scientific Research 2, n^o 12 (1 juin 2012) : 38–41. http://dx.doi.org/10.15373/22778179/dec2013/13.

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Masler, E. P. « In vitrometabolism of an insect neuropeptide by homogenates of the nematodeCaenorhabditis elegans ». Journal of Helminthology 77, n^o 1 (mars 2003) : 43–48. http://dx.doi.org/10.1079/joh2002152.

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AbstractThe cytosolic fraction of homogenates from the free-living soil nematodeCaenorhabditis elegansis capable of metabolizing the insect neuropeptide adipokinetic hormone, a decapeptide blocked at the N-terminus by a pGlu residue. Analysis of digests by RP-HPLC and LC-MS revealed that an initial endoproteolytic cleavage step produced a heptapeptide with an unblocked N-terminus that can serve as a substrate for aminopeptidases. The aminopeptidase activity is depressed in the presence of the inhibitor amastatin; the initial product of the endoproteolytic step accumulates during incubation, and expected aminopeptidase product peptides are reduced in amount, as assessed by chromatographic peak size. The absence of some expected peptide fragments in the reaction mixtures suggests that multiple proteases contribute to short peptide half-lives. Comparison of the adipokinetic hormone digestion inC. elegansto that reported previously for insects reveals the same general pattern of peptide fragment production.

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Marinova, Margarita, Alexander Dolashki, Florian Altenberend, Stefan Stevanovic, Wolfgang Voelter et Bozhidar Tchorbanov. « Characterization of an Aminopeptidase and a Proline Iminopeptidase from Cabbage Leaves ». Zeitschrift für Naturforschung C 63, n^o 1-2 (1 février 2008) : 105–12. http://dx.doi.org/10.1515/znc-2008-1-220.

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Aminopeptidase, preferring phenylalanine-p-nitroanilide as substrate, and proline iminopeptidase, highly-specific for proline-p-nitroanilide, were isolated from cabbage leaves (Brassica oleraceae var. capitata). As pH optima, 7.2−7.5 for aminopeptidase activity and 8.0−8.5 for proline iminopeptidase were determined. Both peptidases were strongly inhibited by p-chloromercuribenzoic acid, heavy metal ions and urea. The molecular weights were determined by gel filtration to be 56 and 204 kDa, respectively. The iminopeptidase was decomposed during SDS electrophoresis to four subunits of 50 kDa. Minor impurities of myrosinase- associated protein (~70 kDa) were found in both preparations. Preliminary data of their amino acid sequences showed similarities to those of aminopeptidases N (family M1) and proline iminopeptidases (family S33).

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Gorvel, J. P., Z. Mishal, F. Liegey, A. Rigal et S. Maroux. « Conformational change of rabbit aminopeptidase N into enterocyte plasma membrane domains analyzed by flow cytometry fluorescence energy transfer. » Journal of Cell Biology 108, n^o 6 (1 juin 1989) : 2193–200. http://dx.doi.org/10.1083/jcb.108.6.2193.

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Membrane vesicle preparations are very appropriate material for studying the topology of glycoproteins integrated into specialized plasma membrane domains of polarized cells. Here we show that the flow cytometric measurement of fluorescence energy transfer used previously to study the relationship between surface components of isolated cells can be applied to membrane vesicles. The fluorescein and rhodamine derivatives of a monoclonal antibody (4H7.1) that recognized one common epitope of the rabbit and pig aminopeptidase N were used for probing the oligomerization and conformational states of the enzyme integrated into the brush border and basolateral membrane vesicles prepared from rabbit and pig enterocytes. The high fluorescent energy transfer observed in the case of pig enzyme integrated into both types of vesicles and in the case of the rabbit enzyme integrated into basolateral membrane vesicles agreed very well with the existence of a dimeric organization, which was directly demonstrated by cross-linking experiments. Although with the latter technique we observed that the rabbit aminopeptidase was also dimerized in the brush border membrane, no energy transfer was detected with the corresponding vesicles. This indicates that the relative positions of two associated monomers differ depending on whether the rabbit aminopeptidase is transiently integrated into the basolateral membrane or permanently integrated into the brush border membrane. Cross-linking of aminopeptidases solubilized by detergent and of their ectodomains liberated by trypsin showed that only interactions between anchor domains maintained the dimeric structure of rabbit enzyme whereas interactions between ectodomains also exist in the pig enzyme. This might explain why the noticeable change in the organization of the two ectodomains observed in the case of rabbit aminopeptidase N does not occur in the case of pig enzyme.

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Zhang, Xian, Chiyu Guan, Yi Hang, Fengdan Liu, Jing Sun, Huifei Yu, Li Gan et al. « An M29 Aminopeptidase from Listeria Monocytogenes Contributes to In Vitro Bacterial Growth but not to Intracellular Infection ». Microorganisms 8, n^o 1 (13 janvier 2020) : 110. http://dx.doi.org/10.3390/microorganisms8010110.

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Aminopeptidases that catalyze the removal of N-terminal residues from polypeptides or proteins are crucial for physiological processes. Here, we explore the biological functions of an M29 family aminopeptidase II from Listeria monocytogenes (LmAmpII). We show that LmAmpII contains a conserved catalytic motif (EEHYHD) that is essential for its enzymatic activity and LmAmpII has a substrate preference for arginine and leucine. Studies on biological roles indicate that LmAmpII is required for in vitro growth in a chemically defined medium for optimal growth of L. monocytogenes but is not required for bacterial intracellular infection in epithelial cells and macrophages, as well as cell-to-cell spreading in fibroblasts. Moreover, LmAmpII is found as dispensable for bacterial pathogenicity in mice. Taken together, we conclude that LmAmpII, an M29 family aminopeptidase, can efficiently hydrolyze a wide range of substrates and is required for in vitro bacterial growth, which lays a foundation for in-depth investigations of aminopeptidases as potential targets to defend Listeria infection.

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John-White, Marietta, Geoff J. Dumsday, Priscilla Johanesen, Dena Lyras, Nyssa Drinkwater et Sheena McGowan. « Crystal structure of a β-aminopeptidase from an AustralianBurkholderiasp. » Acta Crystallographica Section F Structural Biology Communications 73, n^o 7 (17 juin 2017) : 386–92. http://dx.doi.org/10.1107/s2053230x17007737.

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β-Aminopeptidases are a unique group of enzymes that have the unusual capability to hydrolyze N-terminal β-amino acids from synthetic β-peptides. β-Peptides can form secondary structures mimicking α-peptide-like structures that are resistant to degradation by most known proteases and peptidases. These characteristics of β-peptides give them great potential as peptidomimetics. Here, the X-ray crystal structure of BcA5-BapA, a β-aminopeptidase from a Gram-negativeBurkholderiasp. that was isolated from activated sludge from a wastewater-treatment plant in Australia, is reported. The crystal structure of BcA5-BapA was determined to a resolution of 2.0 Å and showed a tetrameric assembly typical of the β-aminopeptidases. Each monomer consists of an α-subunit (residues 1–238) and a β-subunit (residues 239–367). Comparison of the structure of BcA5-BapA with those of other known β-aminopeptidases shows a highly conserved structure and suggests a similar proteolytic mechanism of action.

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Daniel, Anu, Sreedhara Sangadala, Donald H. Dean et Michael J. Adang. « Denaturation of Either Manduca sexta Aminopeptidase N or Bacillus thuringiensis Cry1A Toxins Exposes Binding Epitopes Hidden under Nondenaturing Conditions ». Applied and Environmental Microbiology 68, n^o 5 (mai 2002) : 2106–12. http://dx.doi.org/10.1128/aem.68.5.2106-2112.2002.

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ABSTRACT The effect of polypeptide denaturation of Bacillus thuringiensis Cry1A toxins or purified Manduca sexta 120-kDa aminopeptidase N on the specificities of their interactions was investigated. Ligand and dot blotting experiments were conducted with 125I-labeled Cry1Ac, Cry1Ac mutant 509QNR-AAA511 (QNR-AAA), or 120-kDa aminopeptidase N as the probe. Mutant QNR-AAA does not bind the N-acetylgalactosamine moiety on the 120-kDa aminopeptidase. Both 125I-Cry1Ac and 125I-QNR-AAA bound to 210- and 120-kDa proteins from M. sexta brush border membrane vesicles and purified 120-kDa aminopeptidase N on ligand blots. However, on dot blots 125I-QNR-AAA bound brush border vesicles but did not bind purified aminopeptidase except when aminopeptidase was denatured. In the reciprocal experiment, 125I-aminopeptidase bound Cry1Ac but did not bind QNR-AAA. 125I-aminopeptidase bound Cry1Ab to a limited extent but not the Cry1Ab domain I mutant Y153D or Cry1Ca. However, denatured 125I-aminopeptidase detected each Cry1A toxin and mutant but not Cry1Ca on dot blots. The same pattern of recognition occurred with native (nondenatured) 125I-aminopeptidase probe and denatured toxins as the targets. The broader pattern of toxin-binding protein interaction is probably due to peptide sequences being exposed upon denaturation. Putative Cry toxin-binding proteins identified by the ligand blot technique need to be investigated under native conditions early in the process of identifying binding proteins that may serve as functional toxin receptors.

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Sabat, Pablo, et Sandra P. Gonzalez. « Digestive Enzymes in two Species of Marine Cinclodes (Passeriformes : Furnariidae) ». Condor 105, n^o 4 (1 novembre 2003) : 830–33. http://dx.doi.org/10.1093/condor/105.4.830.

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AbstractChanges in digestive enzyme activity along the intestine may be related to changes in substrate concentration in the intestine. We examined the distribution of digestive enzymes along the intestine in two species of carnivorous passerine birds from the genus Cinclodes. Both species lacked sucrase activity, suggesting that these species are unable to feed on sucrose-rich diets. Distribution of maltase and aminopeptidase-N activity differed from that found in other passerines, including omnivorous species, but resembled those found in herbivorous and frugivorous birds. We hypothesize that the type of prey items that Cinclodes consume may explain the pattern of maltase and aminopeptidase-N expression.Enzimas Digestivas en Dos Especies de Cinclodes Marinos (Passeriformes: Furnariidae)Resumen. Los cambios en los niveles de actividad enzimática digestiva a lo largo del intestino de aves pueden estar relacionados con cambios en la concentración de substratos en el intestino. En este estudio examinamos la distribución de enzimas digestivas a lo largo del intestino en dos especies de aves paseriformes del género Cinclodes. Ambas especies carecen de actividad de sacarasa lo que sugiere que estas especies son incapaces de consumir dietas ricas en sacarosa. La distribución de la actividad de maltasa y aminopeptidasa-N difiere de la documentada para otros paseriformes, incluyendo especies omnívoras, y es similar a la encontrada en aves herbívoras y frugívoras. Se sugiere que el tipo de presas consumidas por Cinclodes explicaría el patrón de expresión de maltasa y aminopeptidasa-N.

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Hooper, N. M., R. J. Hesp et S. Tieku. « Metabolism of aspartame by human and pig intestinal microvillar peptidases ». Biochemical Journal 298, n^o 3 (15 mars 1994) : 635–39. http://dx.doi.org/10.1042/bj2980635.

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The artificial sweetener aspartame (N-L-alpha-aspartyl-L-phenyl-alanine-1-methyl ester; Nutrasweet), its decomposition product alpha Asp-Phe and the related peptide alpha Asp-PheNH2 were rapidly hydrolysed by microvillar membranes prepared from human duodenum, jejunum and ileum, and from pig duodenum and kidney. The metabolism of aspartame by the human and pig intestinal microvillar membrane preparations was inhibited significantly (> 78%) by amastatin or 1,10-phenanthroline, and partially (> 38%) by actinonin or bestatin, and was activated 2.9-4.5-fold by CaCl2. The inhibition by amastatin and 1,10-phenanthroline, and the activation by CaCl2 are characteristic of the cell-surface ectoenzyme aminopeptidase A (EC 3.4.11.7) and a purified preparation of this enzyme hydrolysed aspartame with a Km of 0.25 mM and a Vmax of 126 mumol/min per mg. A purified preparation of aminopeptidase W (EC 3.4.11.16) also hydrolysed aspartame but with a Km of 4.96 mM and a Vmax of 110 mumol/min per mg. However, rentiapril, an inhibitor of aminopeptidase W, caused only slight inhibition (maximally 19%) of the hydrolysis of aspartame by the microvillar membrane preparations. Similar patterns of inhibition and kinetic parameters were observed for alpha Asp-Phe and alpha Asp-PheNH2. Two other decomposition products of aspartame, beta Asp-PheMe and cyclo-Asp-Phe, were essentially resistant to hydrolysis by both the human and pig intestinal microvillar membrane preparations and the purified preparations of aminopeptidases A and W. Although the relatively selective inhibitor of aminopeptidase N (EC 3.4.11.2), actinonin, partially inhibited the metabolism of aspartame, alpha Asp-Phe and alpha Asp-PheNH2 by the human and pig intestinal microvillar membrane preparations, these peptides were not hydrolysed by a purified preparation of aminopeptidase N. Membrane dipeptidase (EC 3.4.13.19) only hydrolysed the unblocked dipeptide, alpha Asp-Phe, but the selective inhibitor of this enzyme, cilastatin, did not block the metabolism of alpha Asp-Phe by the microvillar membrane preparations.

25

Jiang, X., S. Tangada, R. D. Peterson et J. D. Funkhouser. « Expression of aminopeptidase N in fetal rat lung during development ». American Journal of Physiology-Lung Cellular and Molecular Physiology 263, n^o 4 (1 octobre 1992) : L460—L465. http://dx.doi.org/10.1152/ajplung.1992.263.4.l460.

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The ectopeptidase, aminopeptidase N, serves as a cell surface marker of the apical surface of the alveolar type II epithelial cell in adult lung. It is also present in fetal lung before differentiation of morphologically mature type II alveolar epithelial cells, suggesting that it is expressed by precursors of the type II cells. We have examined the mRNA coding for the aminopeptidase in adult and fetal lung and in mature type II cells and determined levels of mRNA and immunoreactive protein during fetal lung development. Comparison of the temporal patterns of steady-state levels of aminopeptidase mRNA and immunoreactive protein during development show that the expression of the protein is developmentally regulated and that expression is regulated, at least in part, at a pretranslational level. Both mRNA and immunoreactive protein levels increase severalfold on the final gestational day, suggesting that the function of the aminopeptidase may be associated with air breathing.

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Melzig, Matthias, et Hedda Bormann. « Betulinic Acid Inhibits Aminopeptidase N Activity ». Planta Medica 64, n^o 07 (octobre 1998) : 655–57. http://dx.doi.org/10.1055/s-2006-957542.

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Ryan, J. W., A. Y. K. Chung, J. A. Nearing, F. A. Valido, S. C. Chen et P. Berryer. « A Radiochemical Assay for Aminopeptidase N ». Analytical Biochemistry 210, n^o 1 (avril 1993) : 27–33. http://dx.doi.org/10.1006/abio.1993.1145.

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Papapetropoulos, Andreas, James W. Ryan, Alexander Antonov, Renu Virmani, Frank D. Kolodgie, Ross G. Gerrity et John D. Catravas. « Human aortic endothelial cell aminopeptidase N ». Immunopharmacology 32, n^o 1-3 (mai 1996) : 153–56. http://dx.doi.org/10.1016/0162-3109(95)00079-8.

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Wang, Xuejian, Lei Zhang, Kanghui Yang, Cai Zhang, Jian Zhang, Hao Fang et Wenfang Xu. « The Effect of Different Species Aminopeptidase N Structure on the Activity Screening of Aminopeptidase N Inhibitor ». Biological & ; Pharmaceutical Bulletin 33, n^o 10 (2010) : 1658–65. http://dx.doi.org/10.1248/bpb.33.1658.

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30

Contreras-Rodriguez, Araceli, Bernardo Ramirez-Zavala, Andrea Contreras, Gerhardt G. Schurig, Nammalwar Sriranganathan et Ahide Lopez-Merino. « Purification and Characterization of an Immunogenic Aminopeptidase of Brucella melitensis ». Infection and Immunity 71, n^o 9 (septembre 2003) : 5238–44. http://dx.doi.org/10.1128/iai.71.9.5238-5244.2003.

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ABSTRACT An immunogenic aminopeptidase was purified from Brucella melitensis strain VTRM1. The purification procedure consisted of ammonium sulfate fractionation and three chromatographic steps. This procedure resulted in a yield of 29% and a 144-fold increase in specific activity. The aminopeptidase appeared to be a monomeric enzyme with a molecular mass of 96 kDa and an isoelectric point of 4.8. Its activity was optimal at pH 7.0 at 40°C. The enzyme was strongly inhibited by EDTA, 1,10-phenathroline, and divalent cations (Zn2+ and Hg2+), suggesting that this protein was a metalloaminopeptidase. The enzyme showed preference for alanine at the N termini of aminoacyl derivatives. The Km values for l-alanine-p-nitroanilide (Ala-pNA) and Lys-pNA were 0.35 and 0.18 mM, respectively. The N-terminal sequence of aminopeptidase was used for a homologous search in the genomes of B. melitensis 16M and Brucella suis 1330. The analysis revealed an exact match of the probe sequence (36 bp) with an open reading frame of 2,652 bp encoding a protein predicted to be alanyl aminopeptidase (aminopeptidase N). Collectively, these data suggest designation of the B. melitensis enzyme as an aminopeptidase N. The aminopeptidase was recognized by sera from patients with acute and chronic brucellosis, suggesting that the enzyme may have important diagnostic implications.

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Ashmun, RA, et AT Look. « Metalloprotease activity of CD13/aminopeptidase N on the surface of human myeloid cells ». Blood 75, n^o 2 (15 janvier 1990) : 462–69. http://dx.doi.org/10.1182/blood.v75.2.462.462.

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Abstract We previously found that the myeloid cell surface glycoprotein CD13 (gp150) is identical to aminopeptidase N (EC 3.4.11.2), a widely distributed membrane-bound, zinc-dependent metalloprotease with an extracellular enzymatic domain that cleaves N-terminal amino acid residues from oligopeptides (J Clin Invest 83:1299, 1989). As a first step toward defining the function of this molecule on myeloid cells, we assessed cell surface-associated N-terminal peptidase activity by sensitive spectrophotometric measurements of the cleavage of p- nitroanilide amino acid derivatives. Aminopeptidase activity detected on the surface of normal and malignant hematopoietic cells coincided with the level of cell surface CD13 expression as measured by flow cytometry. The enzyme was specifically inhibited by the zinc-binding metalloprotease inhibitors, bestatin, 1,10-phenanthroline, or 2.2′- dipyridyl, but was not affected by several inhibitors of other classes of proteases. Aminopeptidase activity was demonstrated for CD13 molecules specifically immunoprecipitated from the surface of CD13- positive cells and was blocked by the metalloprotease inhibitor 1,10- phenanthroline. Moreover, cell surface aminopeptidase activity was partially inhibited when viable cells were incubated with two of a panel of 11 monoclonal antibodies (MoAbs) known to be specific for extracellular epitopes of human CD13. This inhibition was apparent in the absence of detectable downmodulation of CD13 molecules from the cell surface, suggesting that these MoAbs either physically interfere with substrate binding or alter the zinc-coordinating properties of aminopeptidase N molecules. Aminopeptidase N could play an important role in modulating signals generated by peptides at the surface of myeloid cells, either by removing key N-terminal residues from active peptides or by converting inactive peptides to active forms. The inhibitory antibodies used in this study should prove useful in delineating the physiologic roles of CD13/aminopeptidase N on normal and malignant myeloid cells.

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Ashmun, RA, et AT Look. « Metalloprotease activity of CD13/aminopeptidase N on the surface of human myeloid cells ». Blood 75, n^o 2 (15 janvier 1990) : 462–69. http://dx.doi.org/10.1182/blood.v75.2.462.bloodjournal752462.

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We previously found that the myeloid cell surface glycoprotein CD13 (gp150) is identical to aminopeptidase N (EC 3.4.11.2), a widely distributed membrane-bound, zinc-dependent metalloprotease with an extracellular enzymatic domain that cleaves N-terminal amino acid residues from oligopeptides (J Clin Invest 83:1299, 1989). As a first step toward defining the function of this molecule on myeloid cells, we assessed cell surface-associated N-terminal peptidase activity by sensitive spectrophotometric measurements of the cleavage of p- nitroanilide amino acid derivatives. Aminopeptidase activity detected on the surface of normal and malignant hematopoietic cells coincided with the level of cell surface CD13 expression as measured by flow cytometry. The enzyme was specifically inhibited by the zinc-binding metalloprotease inhibitors, bestatin, 1,10-phenanthroline, or 2.2′- dipyridyl, but was not affected by several inhibitors of other classes of proteases. Aminopeptidase activity was demonstrated for CD13 molecules specifically immunoprecipitated from the surface of CD13- positive cells and was blocked by the metalloprotease inhibitor 1,10- phenanthroline. Moreover, cell surface aminopeptidase activity was partially inhibited when viable cells were incubated with two of a panel of 11 monoclonal antibodies (MoAbs) known to be specific for extracellular epitopes of human CD13. This inhibition was apparent in the absence of detectable downmodulation of CD13 molecules from the cell surface, suggesting that these MoAbs either physically interfere with substrate binding or alter the zinc-coordinating properties of aminopeptidase N molecules. Aminopeptidase N could play an important role in modulating signals generated by peptides at the surface of myeloid cells, either by removing key N-terminal residues from active peptides or by converting inactive peptides to active forms. The inhibitory antibodies used in this study should prove useful in delineating the physiologic roles of CD13/aminopeptidase N on normal and malignant myeloid cells.

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Danielsen, E. M., G. M. Cowell, H. Sjöström et O. Norén. « Translational control of an intestinal microvillar enzyme ». Biochemical Journal 235, n^o 2 (15 avril 1986) : 447–51. http://dx.doi.org/10.1042/bj2350447.

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The rates of biosynthesis of adult and foetal pig small-intestinal aminopeptidase N (EC 3.4.11.2) were compared to determine at which level the expression of the microvillar enzyme is developmentally controlled. In organ-cultured explants, the rate of biosynthesis of foetal aminopeptidase N is only about 3% of the adult rate. The small amount synthesized occurs in a high-mannose-glycosylated, membrane-bound, form that is processed to the mature, complex-glycosylated, form at a markedly slower rate than that of the adult enzyme. Extracts of total RNA from adult and foetal intestine contained comparable amounts of aminopeptidase N mRNA, encoding gel-electrophoretically identical primary translation products. Together, these data indicate that the expression of aminopeptidase N is controlled at a translational level.

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Plakidou-Dymock, S., M. J. Tanner et J. D. McGivan. « A role for aminopeptidase N in Na+-dependent amino acid transport in bovine renal brush-border membranes ». Biochemical Journal 290, n^o 1 (15 février 1993) : 59–65. http://dx.doi.org/10.1042/bj2900059.

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A monoclonal antibody FD19 which removes reconstitutable Na(+)-dependent amino acid transport activity from solubilized bovine renal brush-border membrane vesicles was found to react specifically with the enzyme aminopeptidase N. Cleavage of aminopeptidase N from the membranes with papain inhibited Na(+)-dependent amino acid transport activity without affecting that of alpha-methyl D-glucoside. Removal of aminopeptidase substantially increased the Km values for the Na(+)-dependent transport of alanine, glutamine, leucine and phenylalanine without affecting the Vmax. Both Na(+)-dependent amino acid transport and aminopeptidase activity in intact vesicles were competitively inhibited by amino acids with very similar specificity. These results suggest that the amino acid-binding sites of aminopeptidase N and the transporter interact in some way to increase the Km of the transport process for its substrates. However, independent direct inactivation of the transport system by papain cannot be ruled out.

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Chauvel, Eric N., Catherine Llorens-Cortes, Pascale Coric, Sherwin Wilk, Bernard P. Roques et Marie-Claude Fournie-Zaluski. « Differential Inhibition of Aminopeptidase A and Aminopeptidase N by New .beta.-Amino Thiols ». Journal of Medicinal Chemistry 37, n^o 18 (septembre 1994) : 2950–57. http://dx.doi.org/10.1021/jm00044a016.

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36

Tan, Paris S. T., Ingrid J. van Alen-Boerrigter, Bert Poolman, Roland J. Siezen, Willem M. de Vos et W. N. Konings. « Characterization of theLactococcus lactis pepNgene encoding an aminopeptidase homologous to mammalian aminopeptidase N ». FEBS Letters 306, n^o 1 (13 juillet 1992) : 9–16. http://dx.doi.org/10.1016/0014-5793(92)80827-4.

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O'Connell, P. J., V. Gerkis et A. J. d'Apice. « Variable O-glycosylation of CD13 (aminopeptidase N) ». Journal of Biological Chemistry 266, n^o 7 (mars 1991) : 4593–97. http://dx.doi.org/10.1016/s0021-9258(20)64364-2.

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38

Kasman, Laura M. « CD13/aminopeptidase N and murine cytomegalovirus infection ». Virology 334, n^o 1 (mars 2005) : 1–9. http://dx.doi.org/10.1016/j.virol.2005.01.028.

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SENTURK, L., L. GUTIERREZ, F. KAHYAOGLU, E. OZYUREK, M. BAHTIYAR, Z. SENTURK et A. ARICI. « Aminopeptidase N in the human corpus luteum ». Journal of the Society for Gynecologic Investigation 5, n^o 1 (janvier 1998) : 104A. http://dx.doi.org/10.1016/s1071-5576(97)86339-3.

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40

SELI, E., M. BAHTIYAR, L. SENTURK, H. ZEYNELOGLU, D. OLIVE et A. ARICI. « Aminopeptidase N activity in the human endometrium ». Journal of the Society for Gynecologic Investigation 5, n^o 1 (janvier 1998) : 110A. http://dx.doi.org/10.1016/s1071-5576(97)86366-6.

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41

Rangel, R., Y. Sun, L. Guzman-Rojas, M. G. Ozawa, J. Sun, R. J. Giordano, C. S. Van Pelt et al. « Impaired angiogenesis in aminopeptidase N-null mice ». Proceedings of the National Academy of Sciences 104, n^o 11 (7 mars 2007) : 4588–93. http://dx.doi.org/10.1073/pnas.0611653104.

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COWELL, GILIAN M., E. MICHAEL DANIELSEN, HANS SJÖSTRÖM et OVE NORÉN. « Translational control of intestinal microvillar aminopeptidase N ». Biochemical Society Transactions 14, n^o 5 (1 octobre 1986) : 882. http://dx.doi.org/10.1042/bst0140882.

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43

Lucius, Ralph, Jobst Sievers et Rolf Mentlein. « Enkephalin Metabolism by Microglia Aminopeptidase N (CD13) ». Journal of Neurochemistry 64, n^o 4 (23 novembre 2002) : 1841–47. http://dx.doi.org/10.1046/j.1471-4159.1995.64041841.x.

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Dan, Hirohumi, Kenji Tani, Kayoko Hase, Teruki Shimizu, Hiroyuki Tamiya, Yanjmaa Biraa, Luping Huang, Hiroaki Yanagawa et Saburo Sone. « CD13/aminopeptidase N in collagen vascular diseases ». Rheumatology International 23, n^o 6 (12 septembre 2003) : 271–76. http://dx.doi.org/10.1007/s00296-003-0292-5.

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45

Olsen, Jørgen, Hans Sjöström et Ove Norén. « Cloning of the pig aminopeptidase N gene ». FEBS Letters 251, n^o 1-2 (17 juillet 1989) : 275–81. http://dx.doi.org/10.1016/0014-5793(89)81470-x.

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46

VAZEUX, Gilles, Xavier ITURRIOZ, Pierre CORVOL et Catherine LLORENS-CORTES. « A glutamate residue contributes to the exopeptidase specificity in aminopeptidase A ». Biochemical Journal 334, n^o 2 (1 septembre 1998) : 407–13. http://dx.doi.org/10.1042/bj3340407.

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Aminopeptidase A (EC 3.4.11.7, APA) is a 130 kDa membrane-bound aminopeptidase that contains the consensus sequence HEXXH (385–389) found in the zinc metalloprotease family, the zincins. Sequence alignment of the mouse APA with other monozinc-aminopeptidases indicates the presence of a highly conserved glutamate residue (Glu352 in APA) found in the conserved motif GAMEN (349–353). In monozinc-aminopeptidases, the negative charge of the glutamate side-chain carboxylate may constitute the anionic binding site involved in the recognition of the free amino group of substrates or inhibitors. The functional role of Glu352 in APA was investigated by substituting this residue with an aspartate (Asp352), a glycine (Gly352), a glutamine (Gln352) or an arginine (Arg352) residue by site-directed mutagenesis. Kinetic studies showed that the Km values of the mutant enzymes were unaffected, whereas kcat values were decreased 10–250-fold, resulting in a 10-, 30- 260- and 400-fold reduction in cleavage efficiencies for the mutants Asp352, Gly352, Gln352 and Arg352 respectively. The inhibitory potency of two different classes of inhibitors, a thiol and a phosphonate compound, was significantly (P< 0.05) decreased by 10- and 4-fold respectively in the mutated enzymes. Moreover, the inhibitory potency of angiotensin I, used as a competitor of the synthetic substrate α-l-glutamyl β-naphthylamide, displayed a 4-fold reduction (P< 0.01) in the mutated enzymes, whereas the Ki values of its N-acetyl derivative were unchanged. These data strongly suggest that Glu352 is involved in the catalytic process of APA and contributes to the exopeptidase activity of this enzyme through interaction with the N-terminal part of substrates or inhibitors.

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NIRASAWA, Satoru, Yoshiaki NAKAJIMA, Zhen-Zhong ZHANG, Michiteru YOSHIDA et Kiyoshi HAYASHI. « Intramolecular chaperone and inhibitor activities of a propeptide from a bacterial zinc aminopeptidase ». Biochemical Journal 341, n^o 1 (24 juin 1999) : 25–31. http://dx.doi.org/10.1042/bj3410025.

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An aminopeptidase from Aeromonas caviae T-64 was translated as a preproprotein consisting of three domains; a signal peptide (19 amino acid residues), an N-terminal propeptide (101 residues) and a mature region (273 residues). We demonstrated that a proteinase, which was isolated from the culture filtrate of A. caviae T-64, activated the recombinant pro-aminopeptidase by removal of the majority of the propeptide. Using L-Leu-p-nitroanilide as a substrate, the processed aminopeptidase showed a large increase in kcat when compared with the unprocessed enzyme, whereas the Km value remained relatively unchanged. The similar Km values for the pro-aminopeptidase and the mature aminopeptidase indicated that the N-terminal propeptide of the pro-aminopeptidase did not influence the formation of the enzyme-substrate complex, suggesting the absence of marked conformational changes in the active domain. In contrast, the marked difference in kcat suggests a significant decrease in the energy of one or more of the transition states of the enzyme-substrate reaction coordinate. Moreover, we showed that the activity of the urea-denatured pro-aminopeptidase could be recovered by dialysis, whereas the activity of the urea-denatured mature aminopeptidase, which lacked the propeptide, could not. Further to this, the propeptide-deleted aminopeptidase formed an inclusion body in the cytoplasmic space in Escherichia coli and was not secreted at all. These results suggested that the propeptide of the pro-aminopeptidase acted as an intramolecular chaperone that was involved with the correct folding of the enzyme in vitro and was required for extracellular secretion in E. coli.

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Stephens, Elaine, Jane Sugars, Sarah L. Maslen, Dudley H. Williams, Len C. Packman et David J. Ellar. « The N-linked oligosaccharides of aminopeptidase N from Manduca sexta ». European Journal of Biochemistry 271, n^o 21 (20 octobre 2004) : 4241–58. http://dx.doi.org/10.1111/j.1432-1033.2004.04364.x.

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McDONNELL, MAEVE, RICHARD FITZGERALD, IDE NI FHAOLÁIN, P. VINCENT JENNINGS et GERARD O'CUINN. « Purification and characterization of aminopeptidase P from Lactococcus lactis subsp. cremoris ». Journal of Dairy Research 64, n^o 3 (août 1997) : 399–407. http://dx.doi.org/10.1017/s0022029997002318.

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Aminopeptidase P was purified 65·3-fold from the cytoplasm of Lactococcus lactis subsp. cremoris AM2 with a 5·8% yield. The purified enzyme was found to consist of one polypeptide chain with a relative molecular mass of 41600. Metal chelating agents were found to be inhibitory and Mn2+ and Co2+ stimulated activity 7-fold and 6-fold respectively. The purified enzyme removed the N-terminal amino acid from peptides only where proline (and in one case alanine) was present in the penultimate position. No hydrolysis was observed either with dipeptides even when proline was present in the C-terminal position or when either N-terminal proline or pyroglutamate was present preceding a proline residue in the penultimate position of longer peptides. On the basis of this substrate specificity either aminopeptidase P or post-proline dipeptidyl aminopeptidase are necessary along with a broad specificity aminopeptidase to effect complete hydrolysis of casein-derived peptides containing a single internally placed proline residue. However, both aminopeptidase P and post-proline dipeptidyl aminopeptidase would be required together with a broad specificity aminopeptidase in order to completely hydrolyse casein-derived peptides that contain two internally placed consecutive proline residues. As bitter casein-derived peptides are likely to contain either single prolines or pairs of prolines, aminopeptidase P appears to be an important enzyme for debittering.

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Danielsen, E. M. « Tyrosine sulphation is not required for microvillar expression of intestinal aminopeptidase N ». Biochemical Journal 254, n^o 1 (15 août 1988) : 219–22. http://dx.doi.org/10.1042/bj2540219.

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The effect of 2,6-dichloro-4-nitrophenol (DCNP), an inhibitor of phenol sulphotransferases (EC 2.8.2.-), on the biosynthesis of aminopeptidase N (EC 3.4.11.2) was studied in organ-cultured pig intestinal mucosal explants. At 50 microM DCNP did not affect protein synthesis but it decreased incorporation of [35S]sulphate into aminopeptidase N and other major microvillar hydrolases by 70-85% compared with controls, indicating an inhibition of their post-translational tyrosine sulphation. In labelling experiments with [35S]methionine from 0.5 to 5 h, DCNP was tested for its possible influence on synthesis, processing and microvillar expression of aminopeptidase N, but no effect on any of these parameters could be detected. It can therefore be concluded that tyrosine sulphation is not required (for instance as a sorting signal) for the targeting of newly synthesized enzymes to the microvillar membrane.

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