Journal articles: 'Enzyme kinetics'

1

Guerrieri, Antonio, Rosanna Ciriello, Giuliana Bianco, Francesca De Gennaro, and Silvio Frascaro. "Allosteric Enzyme-Based Biosensors—Kinetic Behaviours of Immobilised L-Lysine-α-Oxidase from Trichoderma viride: pH Influence and Allosteric Properties." Biosensors 10, no. 10 (October 17, 2020): 145. http://dx.doi.org/10.3390/bios10100145.

Full text

Abstract:

The present study describes the kinetics of L-lysine-α-oxidase (LO) from Trichoderma viride immobilised by co-crosslinking onto the surface of a Pt electrode. The resulting amperometric biosensor was able to analyse L-lysine, thus permitting a simple but thorough study of the kinetics of the immobilised enzyme. The kinetic study evidenced that LO behaves in an allosteric fashion and that cooperativity is strongly pH-dependent. Not less important, experimental evidence shows that cooperativity is also dependent on substrate concentration at high pH and behaves as predicted by the Monod-Wyman-Changeux model for allosteric enzymes. According to this model, the existence of two different conformational states of the enzyme was postulated, which differ in Lys species landing on LO to form the enzyme–substrate complex. Considerations about the influence of the peculiar LO kinetics on biosensor operations and extracorporeal reactor devices will be discussed as well. Not less important, the present study also shows the effectiveness of using immobilised enzymes and amperometric biosensors not only for substrate analysis, but also as a convenient tool for enzyme kinetic studies.

APA, Harvard, Vancouver, ISO, and other styles

2

Moe, Owen, and Richard Cornelius. "Enzyme kinetics." Journal of Chemical Education 65, no. 2 (February 1988): 137. http://dx.doi.org/10.1021/ed065p137.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Herries, D. G. "Enzyme Kinetics." Biochemical Education 16, no. 3 (July 1988): 179–80. http://dx.doi.org/10.1016/0307-4412(88)90207-5.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

H.B.F.D. "Enzyme kinetics." Trends in Biochemical Sciences 13, no. 10 (October 1988): 411. http://dx.doi.org/10.1016/0968-0004(88)90200-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

WAGG, JONATHAN, and PETER H. SELLERS. "Enzyme Kinetics." Annals of the New York Academy of Sciences 779, no. 1 (April 1996): 272–78. http://dx.doi.org/10.1111/j.1749-6632.1996.tb44793.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Lloyd, Matthew D. "Steady-state enzyme kinetics." Biochemist 43, no. 3 (May 10, 2021): 40–45. http://dx.doi.org/10.1042/bio_2020_109.

Full text

Abstract:

Steady-state enzyme kinetics is a cornerstone technique of biochemistry and related sciences since it allows the characterization and quantification of enzyme behaviour. Enzyme kinetics is widely used to investigate the physiological role of enzymes, determine the effects of mutations and characterize enzyme inhibitors. Well-known examples of enzyme inhibitors used to treat diseases include anti-infectives (e.g., penicillin, clavulanic acid and HIV protease inhibitors); anti-inflammatories (e.g., aspirin and ibuprofen); cholesterol-lowering statins; tyrosine kinase inhibitors used to treat cancer; and Viagra. Commonly, new disease treatments are discovered by using enzyme kinetics to identify the few active compounds residing within a large compound collection (‘high-throughput screening’). The subject of enzyme kinetics is typically introduced to first-year undergraduates with a mathematical description of behaviour. This Beginners Guide will give a brief overview of experimental enzyme kinetics and the characterization of enzyme inhibitors. Colorimetric assays using a microtitre plate will be considered, although most principles also apply to other assays.

APA, Harvard, Vancouver, ISO, and other styles

7

Markin, C. J., D. A. Mokhtari, F. Sunden, M. J. Appel, E. Akiva, S. A. Longwell, C. Sabatti, D. Herschlag, and P. M. Fordyce. "Revealing enzyme functional architecture via high-throughput microfluidic enzyme kinetics." Science 373, no. 6553 (July 22, 2021): eabf8761. http://dx.doi.org/10.1126/science.abf8761.

Full text

Abstract:

Systematic and extensive investigation of enzymes is needed to understand their extraordinary efficiency and meet current challenges in medicine and engineering. We present HT-MEK (High-Throughput Microfluidic Enzyme Kinetics), a microfluidic platform for high-throughput expression, purification, and characterization of more than 1500 enzyme variants per experiment. For 1036 mutants of the alkaline phosphatase PafA (phosphate-irrepressible alkaline phosphatase of Flavobacterium), we performed more than 670,000 reactions and determined more than 5000 kinetic and physical constants for multiple substrates and inhibitors. We uncovered extensive kinetic partitioning to a misfolded state and isolated catalytic effects, revealing spatially contiguous regions of residues linked to particular aspects of function. Regions included active-site proximal residues but extended to the enzyme surface, providing a map of underlying architecture not possible to derive from existing approaches. HT-MEK has applications that range from understanding molecular mechanisms to medicine, engineering, and design.

APA, Harvard, Vancouver, ISO, and other styles

8

Martín, J., J. Pérez-Gil, C. Acebal, and R. Arche. "Theoretical approach to the steady-state kinetics of a bi-substrate acyl-transfer enzyme reaction that follows a hydrolysable-acyl-enzyme-based mechanism. Application to the study of lysophosphatidylcholine:lysophosphatidylcholine acyltransferase from rabbit lung." Biochemical Journal 266, no. 1 (February 15, 1990): 47–53. http://dx.doi.org/10.1042/bj2660047.

Full text

Abstract:

A kinetic model is proposed for catalysis by an enzyme that has several special characteristics: (i) it catalyses an acyl-transfer bi-substrate reaction between two identical molecules of substrate, (ii) the substrate is an amphiphilic molecule that can be present in two physical forms, namely monomers and micelles, and (iii) the reaction progresses through an acyl-enzyme-based mechanism and the covalent intermediate can react also with water to yield a secondary hydrolytic reaction. The theoretical kinetic equations for both reactions were deduced according to steady-state assumptions and the theoretical plots were predicted. The experimental kinetics of lysophosphatidylcholine:lysophosphatidylcholine acyltransferase from rabbit lung fitted the proposed equations with great accuracy. Also, kinetics of inhibition by products behaved as expected. It was concluded that the competition between two nucleophiles for the covalent acyl-enzyme intermediate, and not a different enzyme action depending on the physical state of the substrate, is responsible for the differences in kinetic pattern for the two activities of the enzyme. This conclusion, together with the fact that the kinetic equation for the transacylation is quadratic, generates a ‘hysteretic’ pattern that can provide the basis of self-regulatory properties for enzymes to which this model could be applied.

APA, Harvard, Vancouver, ISO, and other styles

9

WU, Jia-Wei, Zhi-Xin WANG, and Jun-Mei ZHOU. "Inactivation kinetics of dihydrofolate reductase from Chinese hamster during urea denaturation." Biochemical Journal 324, no. 2 (June 1, 1997): 395–401. http://dx.doi.org/10.1042/bj3240395.

Full text

Abstract:

The kinetic theory of substrate reaction during modification of enzyme activity has been applied to the study of inactivation kinetics of Chinese hamster dihydrofolate reductase by urea [Tsou (1988) Adv. Enzymol. Relat. Areas Mol. Biol. 61, 381–436]. On the basis of the kinetic equation of substrate reaction in the presence of urea, all microscopic kinetic constants for the free enzyme and enzyme–substrate binary and ternary complexes have been determined. The results of the present study indicate that the denaturation of dihydrofolate reductase by urea follows single-phase kinetics, and changes in enzyme activity and tertiary structure proceed simultaneously in the unfolding process. Both substrates, NADPH and 7,8-dihydrofolate, protect dihydrofolate reductase against inactivation, and enzyme–substrate complexes lose their activity less rapidly than the free enzyme.

APA, Harvard, Vancouver, ISO, and other styles

10

Meilany, Diah, Efri Mardawati, Made Tri Ari Penia Kresnowati, and Tjandra Setiadi. "KINETIC STUDY OF OIL PALM EMPTY FRUIT BUNCH ENZYMATIC HYDROLYSIS." Reaktor 17, no. 4 (February 2, 2018): 197. http://dx.doi.org/10.14710/reaktor.17.4.197-202.

Full text

Abstract:

As lignocellulosic biomass, Oil Palm Empty Fruit Bunch (OPEFB) can be used as the source of xylose that can be further utilized as the raw material for xylitol production. The processing of OPEFB to xylose comprises of pretreatment and hydrolysis that can be performed enzymatically. This process offers the advantages of moderate operation conditions and more environmentally friendly. This article describes the kinetic study of enzymatic hydrolysis process of OPEFB for producing xylose using self-prepared and commercial xylanase enzymes. Despite the possible mass transfer limitation, the Michaelis Menten kinetics was hypothesized. The results indicated that the reaction at pH 5 and 60°C followed the Michaelis Menten kinetics, with Vm of 0.84 g/L-h and Km of 48.5 g/L for the commercial enzyme, and Vm of 0,38 g/L-h and Km of 0,37 g/L for the self-prepared enzyme. The reaction is affected by temperature, with Ea of 8.6 kcal/gmol. The performance of self-prepared xylanase enzyme was not yet as good as the commercial enzyme, Cellic Htec 2. Keywords: enzymatic hydrolysis; kinetics parameter; OPEFB; xylanase; xylose

APA, Harvard, Vancouver, ISO, and other styles

11

Chisti, Yusuf. "Understanding enzyme kinetics." Biotechnology Advances 20, no. 5-6 (December 2002): 425–26. http://dx.doi.org/10.1016/s0734-9750(02)00028-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Gutfreund, H. "Basic enzyme kinetics." FEBS Letters 212, no. 1 (February 9, 1987): 178. http://dx.doi.org/10.1016/0014-5793(87)81582-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Louisot, P. "Basic enzyme kinetics." Biochimie 69, no. 5 (May 1987): 556–57. http://dx.doi.org/10.1016/0300-9084(87)90099-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Cornish-Bowden, Athel. "Encyclopaedic enzyme kinetics." Trends in Biochemical Sciences 19, no. 3 (March 1994): 142. http://dx.doi.org/10.1016/0968-0004(94)90211-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Tang, J. Y. "On the relationships between Michaelis–Menten kinetics, reverse Michaelis–Menten kinetics, Equilibrium Chemistry Approximation kinetics and quadratic kinetics." Geoscientific Model Development Discussions 8, no. 9 (September 3, 2015): 7663–91. http://dx.doi.org/10.5194/gmdd-8-7663-2015.

Full text

Abstract:

Abstract. The Michaelis–Menten kinetics and the reverse Michaelis–Menten kinetics are two popular mathematical formulations used in many land biogeochemical models to describe how microbes and plants would respond to changes in substrate abundance. However, the criteria of when to use which of the two are often ambiguous. Here I show that these two kinetics are special approximations to the Equilibrium Chemistry Approximation kinetics, which is the first order approximation to the quadratic kinetics that solves the equation of enzyme-substrate complex exactly for a single enzyme single substrate biogeochemical reaction with the law of mass action and the assumption of quasi-steady-state for the enzyme-substrate complex and that the product genesis from enzyme-substrate complex is much slower than the equilibration between enzyme-substrate complexes, substrates and enzymes. In particular, I showed that the derivation of the Michaelis–Menten kinetics does not consider the mass balance constraint of the substrate, and the reverse Michaelis–Menten kinetics does not consider the mass balance constraint of the enzyme, whereas both of these constraints are taken into account in the Equilibrium Chemistry Approximation kinetics. By benchmarking against predictions from the quadratic kinetics for a wide range of substrate and enzyme concentrations, the Michaelis–Menten kinetics was found to persistently under-predict the normalized sensitivity ∂ ln v / ∂ ln k2+ of the reaction velocity v with respect to the maximum product genesis rate k2+, persistently over-predict the normalized sensitivity ∂ ln v / ∂ ln k1+ of v with respect to the intrinsic substrate affinity k1+, persistently over-predict the normalized sensitivity ∂ ln v / ∂ ln [ E ]T of v with respect the total enzyme concentration [ E ]T and persistently under-predict the normalized sensitivity ∂ ln v / ∂ ln [ S ]T of v with respect to the total substrate concentration [ S ]T. Meanwhile, the reverse Michaelis–Menten kinetics persistently under-predicts ∂ ln v / ∂ ln k2+ and ∂ ln v / ∂ ln [ E ]T, and persistently over-predicts ∂ ln v / ∂ ln k1+ and ∂ ln v / ∂ ln [ S ]T. In contrast, the Equilibrium Chemistry Approximation kinetics always gives consistent predictions of ∂ ln v / ∂ ln k2+, ∂ ln v / ∂ ln k1+, ∂ ln v / ∂ ln [ E ]T and ∂ ln v / ∂ ln [ S ]T. Since the Equilibrium Chemistry Approximation kinetics includes the advantages from both the Michaelis–Menten kinetics and the reverse Michaelis–Menten kinetics and it is applicable for almost the whole range of substrate and enzyme abundances, soil biogeochemical modelers therefore no longer need to choose when to use the Michaelis–Menten kinetics or the reverse Michaelis–Menten kinetics. I expect removing this choice ambiguity will make it easier to formulate more robust and consistent land biogeochemical models.

APA, Harvard, Vancouver, ISO, and other styles

16

Fink, A. M. "Optimal control in liver kinetics." Journal of the Australian Mathematical Society. Series B. Applied Mathematics 27, no. 3 (January 1986): 361–69. http://dx.doi.org/10.1017/s0334270000004987.

Full text

Abstract:

AbstractWe solve a minimization problem in liver kinetics posed by Bass, et al., in this journal, (1984), pages 538–562. The problem is to choose the density functions for the location of two enzymes, in order to minimize the concentration of an intermediate form of a substance at the outlet of the liver. This form may be toxic to the rest of the body, but the second enzyme renders it harmless. It seems natural that the second enzyme should be downstream from the first. However, we can show that the minimum problem is sometimes solved by an overlap of the supports of the two density functions. Even more surprising is that, for certain forms of the kinetic functions and high levels of transformation of the first enzymatic reaction, some of the first enzyme should be located downstream from all the second enzyme. This suggests that the first reaction should be relatively slow.

APA, Harvard, Vancouver, ISO, and other styles

17

Schnell, S. "Enzyme Kinetics at High Enzyme Concentration." Bulletin of Mathematical Biology 62, no. 3 (May 2000): 483–99. http://dx.doi.org/10.1006/bulm.1999.0163.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Dusíková, Adriána, Timea Baranová, Ján Krahulec, Olívia Dakošová, Ján Híveš, Monika Naumowicz, and Miroslav Gál. "Electrochemical Impedance Spectroscopy for the Sensing of the Kinetic Parameters of Engineered Enzymes." Sensors 24, no. 8 (April 20, 2024): 2643. http://dx.doi.org/10.3390/s24082643.

Full text

Abstract:

The study presents a promising approach to enzymatic kinetics using Electrochemical Impedance Spectroscopy (EIS) to assess fundamental parameters of modified enteropeptidases. Traditional methods for determining these parameters, while effective, often lack versatility and convenience, especially under varying environmental conditions. The use of EIS provides a novel approach that overcomes these limitations. The enteropeptidase underwent genetic modification through the introduction of single amino acid modifications to assess their effect on enzyme kinetics. However, according to the one-sample t-test results, the difference between the engineered enzymes and hEKL was not statistically significant by conventional criteria. The kinetic parameters were analyzed using fluorescence spectroscopy and EIS, which was found to be an effective tool for the real-time measurement of enzyme kinetics. The results obtained through EIS were not significantly different from those obtained through traditional fluorescence spectroscopy methods (p value >> 0.05). The study validates the use of EIS for measuring enzyme kinetics and provides insight into the effects of specific amino acid changes on enteropeptidase function. These findings have potential applications in biotechnology and biochemical research, suggesting a new method for rapidly assessing enzymatic activity.

APA, Harvard, Vancouver, ISO, and other styles

19

Tang, J. Y. "On the relationships between the Michaelis–Menten kinetics, reverse Michaelis–Menten kinetics, equilibrium chemistry approximation kinetics, and quadratic kinetics." Geoscientific Model Development 8, no. 12 (December 1, 2015): 3823–35. http://dx.doi.org/10.5194/gmd-8-3823-2015.

Full text

Abstract:

Abstract. The Michaelis–Menten kinetics and the reverse Michaelis–Menten kinetics are two popular mathematical formulations used in many land biogeochemical models to describe how microbes and plants would respond to changes in substrate abundance. However, the criteria of when to use either of the two are often ambiguous. Here I show that these two kinetics are special approximations to the equilibrium chemistry approximation (ECA) kinetics, which is the first-order approximation to the quadratic kinetics that solves the equation of an enzyme–substrate complex exactly for a single-enzyme and single-substrate biogeochemical reaction with the law of mass action and the assumption of a quasi-steady state for the enzyme–substrate complex and that the product genesis from enzyme–substrate complex is much slower than the equilibration between enzyme–substrate complexes, substrates, and enzymes. In particular, I show that the derivation of the Michaelis–Menten kinetics does not consider the mass balance constraint of the substrate, and the reverse Michaelis–Menten kinetics does not consider the mass balance constraint of the enzyme, whereas both of these constraints are taken into account in deriving the equilibrium chemistry approximation kinetics. By benchmarking against predictions from the quadratic kinetics for a wide range of substrate and enzyme concentrations, the Michaelis–Menten kinetics was found to persistently underpredict the normalized sensitivity ∂ ln v / ∂ ln k2+ of the reaction velocity v with respect to the maximum product genesis rate k2+, persistently overpredict the normalized sensitivity ∂ ln v / ∂ ln k1+ of v with respect to the intrinsic substrate affinity k1+, persistently overpredict the normalized sensitivity ∂ ln v / ∂ ln [E]T of v with respect the total enzyme concentration [E]T, and persistently underpredict the normalized sensitivity ∂ ln v / ∂ ln [S]T of v with respect to the total substrate concentration [S]T. Meanwhile, the reverse Michaelis–Menten kinetics persistently underpredicts ∂ ln v / ∂ ln k2+ and ∂ ln v / ∂ ln [E]T, and persistently overpredicts ∂ ln v / ∂ ln k1+ and ∂ ln v / ∂ ln [S]T. In contrast, the equilibrium chemistry approximation kinetics always gives consistent predictions of ∂ ln v / ∂ ln k2+, ∂ ln v / ∂ ln k1+, ∂ ln v / ∂ ln [E]T, and ∂ ln v / ∂ ln [S]T, indicating that ECA-based models will be more calibratable if the modeled processes do obey the law of mass action. Since the equilibrium chemistry approximation kinetics includes advantages from both the Michaelis–Menten kinetics and the reverse Michaelis–Menten kinetics and it is applicable for almost the whole range of substrate and enzyme abundances, land biogeochemical modelers therefore no longer need to choose when to use the Michaelis–Menten kinetics or the reverse Michaelis–Menten kinetics. I expect that removing this choice ambiguity will make it easier to formulate more robust and consistent land biogeochemical models.

APA, Harvard, Vancouver, ISO, and other styles

20

Romaní, A. M. "Characterization of extracellular enzyme kinetics in two Mediterranean streams." Fundamental and Applied Limnology 148, no. 1 (April 13, 2000): 99–117. http://dx.doi.org/10.1127/archiv-hydrobiol/148/2000/99.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Pyne, N. J., M. E. Cooper, and M. D. Houslay. "Identification and characterization of both the cytosolic and particulate forms of cyclic GMP-stimulated cyclic AMP phosphodiesterase from rat liver." Biochemical Journal 234, no. 2 (March 1, 1986): 325–34. http://dx.doi.org/10.1042/bj2340325.

Full text

Abstract:

Two enzymes displaying cyclic GMP-stimulated cyclic AMP phosphodiesterase activity were purified from rat liver to apparent homogeneity: a ‘particulate enzyme’ found as an integral membrane protein associated with the plasma membrane, and a ‘soluble’ enzyme found in the cytosol. The physical properties of these enzymes were very similar, being dimers of Mr 134,000, composed in each instance of two subunits of Mr = 66,000-67,000. Both enzymes showed similar kinetics for cyclic AMP hydrolysis. They are both high-affinity enzymes, with kinetic constants for the particulate enzyme of Km = 34 microM and Vmax. = 4.0 units/mg of protein and for the cytosolic enzyme Km = 40 microM and Vmax. = 4.8 units/mg of protein. In both instances hydrolysis of cyclic AMP appeared to show apparent positive co-operativity, with Hill coefficients (happ.) of 1.5 and 1.6 for the particulate and cytosolic enzymes respectively. However, in the presence of 2 microM-cyclic GMP, the hydrolysis of cyclic AMP obeyed Michaelis kinetics (happ. = 1) for both enzymes. The addition of micromolar concentrations of cyclic GMP had little effect on the Vmax. for cyclic AMP hydrolysis, but lowered the Km for cyclic AMP hydrolysis to around 20 microM in both cases. However, at low cyclic AMP substrate concentrations, cyclic GMP was a more potent activator of the particulate enzyme than was the soluble enzyme. The activity of these enzymes could be selectively inhibited by cis-16-palmitoleic acid and by arachidonic acid. In each instance, however, the hydrolysis of cyclic AMP became markedly more sensitive to such inhibition when low concentrations of cyclic GMP were present. Tryptic peptide maps of iodinated preparations of these two purified enzyme species showed that there was considerable homology between these two enzyme forms.

APA, Harvard, Vancouver, ISO, and other styles

22

Crabbe, M. James C., and Derek Goode. "Nonlinear steady-state kinetics of chloramphenicol acetyltransferase." Biochemistry and Cell Biology 69, no. 9 (September 1, 1991): 630–34. http://dx.doi.org/10.1139/o91-093.

Full text

Abstract:

Steady-state kinetic analysis of chloramphenicol acetyltransferase showed that medium effects (higher temperatures or pH, higher ionic strengths, or lower values for dielectric constant) altered the kinetic behaviour of the enzyme with acetyl-CoA as substrate, but did not significantly affect behaviour with chloramphenicol. This was manifest as an increase in the degree of the rate equation to a 2:2 function. This is interpreted in terms of perturbations to the enzyme at or near the acetyl-CoA binding region of the enzyme.Key words: acetyl coenzyme A, chloramphenicol, antibiotics, enzyme kinetics.

APA, Harvard, Vancouver, ISO, and other styles

23

Blackmore, R. S., T. Brittain, and C. Greenwood. "An analysis of the reaction kinetics of the hexahaem nitrite reductase of the anaerobic rumen bacterium Wolinella succinogenes." Biochemical Journal 271, no. 2 (October 15, 1990): 457–61. http://dx.doi.org/10.1042/bj2710457.

Full text

Abstract:

The reduction kinetics of both the resting and redox-cycled forms of the nitrite reductase from the anaerobic rumen bacterium Wolinella succinogenes were studied by stopped-flow reaction techniques. Single-turnover reduction of the enzyme by dithionite occurs in two kinetic phases for both forms of the enzyme. When the resting form of the enzyme is subjected to a single-turnover reduction by dithionite, the slower of the two kinetic phases exhibits a hyperbolic dependence of the rate constant on the square root of the reductant concentration, the limiting value of which (approximately 4 s-1) is assigned to a slow internal electron-transfer process. In contrast, when the redox-cycled form of the enzyme is reduced by dithionite in a single-turnover experiment, both kinetic phases exhibit linear dependences of the rate on the square root of dithionite concentration, with associated rate constants of 150 M-1/2.s-1 and 6 M-1/2.s-1. Computer simulations of both the reduction processes shows that no unique set of rate constants can account for the kinetics of both forms, although the kinetics of the redox-cycled species is consistent with a much enhanced rate of internal electron transfer. Under turnover conditions the time course for reduction of the enzyme, in the presence of millimolar levels of nitrite and 100 mM-dithionite, is extremely complex. A working model for the mechanism of the turnover activity of the enzyme is proposed which very closely describes the reaction kinetics over a wide range of substrate concentrations, as shown by computer simulation. The similarity in the action of the nitrite reductase enzyme and mammalian cytochrome c oxidase is commented upon.

APA, Harvard, Vancouver, ISO, and other styles

24

Wang, Z. X., H. B. Wu, X. C. Wang, H. M. Zhou, and C. L. Tsou. "Kinetics of the course of inactivation of aminoacylase by 1,10-phenanthroline." Biochemical Journal 281, no. 1 (January 1, 1992): 285–90. http://dx.doi.org/10.1042/bj2810285.

Full text

Abstract:

The kinetic theory of the substrate reaction during modification of enzyme activity previously described [Tsou (1988) Adv. Enzymol. Relat. Areas Mol. Biol. 61, 381-436] has been applied to a study on the kinetics of the course of inactivation of aminoacylase by 1,10-phenanthroline. Upon dilution of the enzyme that had been incubated with 1,10-phenanthroline into the reaction mixture, the activity of the inhibited enzyme gradually increased, indicating dissociation of a reversible enzyme–1,10-phenanthroline complex. The kinetics of the substrate reaction with different concentrations of the substrate chloroacetyl-L-alanine and the inactivator suggest a complexing mechanism for inactivation by, and substrate competition with, 1,10-phenanthroline at the active site. The inactivation kinetics are single phasic, showing that the initial formation of an enzyme-Zn(2+)-1,10-phenanthroline complex is a relatively rapid reaction, followed by a slow inactivation step that probably involves a conformational change of the enzyme. The presence of Zn2+ apparently stabilizes an active-site conformation required for enzyme activity.

APA, Harvard, Vancouver, ISO, and other styles

25

Duskey, Jason Thomas, Federica da Ros, Ilaria Ottonelli, Barbara Zambelli, Maria Angela Vandelli, Giovanni Tosi, and Barbara Ruozi. "Enzyme Stability in Nanoparticle Preparations Part 1: Bovine Serum Albumin Improves Enzyme Function." Molecules 25, no. 20 (October 9, 2020): 4593. http://dx.doi.org/10.3390/molecules25204593.

Full text

Abstract:

Enzymes have gained attention for their role in numerous disease states, calling for research for their efficient delivery. Loading enzymes into polymeric nanoparticles to improve biodistribution, stability, and targeting in vivo has led the field with promising results, but these enzymes still suffer from a degradation effect during the formulation process that leads to lower kinetics and specific activity leading to a loss of therapeutic potential. Stabilizers, such as bovine serum albumin (BSA), can be beneficial, but the knowledge and understanding of their interaction with enzymes are not fully elucidated. To this end, the interaction of BSA with a model enzyme B-Glu, part of the hydrolase class and linked to Gaucher disease, was analyzed. To quantify the natural interaction of beta-glucosidase (B-Glu,) and BSA in solution, isothermal titration calorimetry (ITC) analysis was performed. Afterwards, polymeric nanoparticles encapsulating these complexes were fully characterized, and the encapsulation efficiency, activity of the encapsulated enzyme, and release kinetics of the enzyme were compared. ITC results showed that a natural binding of 1:1 was seen between B-Glu and BSA. Complex concentrations did not affect nanoparticle characteristics which maintained a size between 250 and 350 nm, but increased loading capacity (from 6% to 30%), enzyme activity, and extended-release kinetics (from less than one day to six days) were observed for particles containing higher B-Glu:BSA ratios. These results highlight the importance of understanding enzyme:stabilizer interactions in various nanoparticle systems to improve not only enzyme activity but also biodistribution and release kinetics for improved therapeutic effects. These results will be critical to fully characterize and compare the effect of stabilizers, such as BSA with other, more relevant therapeutic enzymes for central nervous system (CNS) disease treatments.

APA, Harvard, Vancouver, ISO, and other styles

26

DE ATAURI, Pedro, Luis ACERENZA, Boris N. KHOLODENKO, Núria DE LA IGLESIA, Joan J. GUINOVART, Loranne AGIUS, and Marta CASCANTE. "Occurrence of paradoxical or sustained control by an enzyme when overexpressed: necessary conditions and experimental evidence with regard to hepatic glucokinase." Biochemical Journal 355, no. 3 (April 24, 2001): 787–93. http://dx.doi.org/10.1042/bj3550787.

Full text

Abstract:

It is widely assumed that the control coefficient of an enzyme on pathway flux decreases as the concentration of enzyme increases. However, it has been shown [Kholodenko and Brown (1996) Biochem. J. 314, 753–760] that enzymes with sigmoidal kinetics can maintain or even gain control with an increase in enzyme activity or concentration. This has been described as ‘paradoxical control’. Here we formulate the general requirements for allosteric enzyme kinetics to display this behaviour. We show that a necessary condition is that the Hill coefficient of the enzyme should increase with an increase in substrate concentration or decrease with an increase in product concentration. We also describe the necessary and sufficient requirements for the occurrence of paradoxical control in terms of the flux control coefficients and the derivatives of the elasticities. The derived expression shows that the higher the control coefficient of an allosteric enzyme, the more likely it is that the pathway will display this behaviour. Control of pathway flux is generally shared between a large number of enzymes and therefore the likelihood of observing sustained or increased control is low, even if the kinetic parameters are in the most favourable range to generate the phenomenon. We show that hepatic glucokinase, which has a very high flux control coefficient and displays sigmoidal behaviour within the hepatocyte in situ as a result of interaction with a regulatory protein, displays sustained or increased control over an extended range of enzyme concentrations when the regulatory protein is overexpressed.

APA, Harvard, Vancouver, ISO, and other styles

27

WANG, Ming-Hua, Zhi-Xin WANG, and Kang-Yuan ZHAO. "Kinetics of inactivation of bovine pancreatic ribonuclease A by bromopyruvic acid." Biochemical Journal 320, no. 1 (November 15, 1996): 187–92. http://dx.doi.org/10.1042/bj3200187.

Full text

Abstract:

The kinetic theory of substrate reaction during the modification of enzyme activity [Duggleby (1986) J. Theor. Biol. 123, 67–80; Wang and Tsou (1990) J. Theor. Biol. 142, 531–549] has been applied to a study of the inactivation kinetics of ribonuclease A by bromopyruvic acid. The results show that irreversible inhibition belongs to a non-competitive complexing type inhibition. On the basis of the kinetic equation of substrate reaction in the presence of the inhibitor, all microscopic kinetic constants for the free enzyme, the enzyme–substrate complex and the enzyme–product complex have been determined. The non-competitive inhibition type indicates that neither the substrate nor the product affects the binding of bromopyruvic acid to the enzyme and that the ionization state of His-119 may be the same in both the enzyme–substrate and the enzyme–product complexes.

APA, Harvard, Vancouver, ISO, and other styles

28

Vannoy, Kathryn J., Andrey Ryabykh, Andrei I. Chapoval, and Jeffrey E. Dick. "Single enzyme electroanalysis." Analyst 146, no. 11 (2021): 3413–21. http://dx.doi.org/10.1039/d1an00230a.

Full text

Abstract:

Traditional enzymology relies on the kinetics of millions of enzymes, an experimental approach that may wash out heterogeneities between individual enzymes. Electrochemical methods have emerged in the last 5 years to probe single enzyme reactivity.

APA, Harvard, Vancouver, ISO, and other styles

29

Valchev, Ivo, Nikolay Yavorov, and Stoyko Petrin. "Topochemical kinetic mechanism of cellulase hydrolysis on fast-growing tree species. COST Action FP1105." Holzforschung 70, no. 12 (December 1, 2016): 1147–53. http://dx.doi.org/10.1515/hf-2016-0030.

Full text

Abstract:

Abstract Optimization of the lignocellulosic bioconversion by cellulolytic enzymes requires good knowledge of reaction kinetics. In the present paper, the investigations of the kinetics have been performed on the fast-growing tree species of poplar, paulownia, willow and black locust, which were pretreated by steam explosion (SE), and bleached kraft pulp (BKP) made of a hardwood mixture. The applicability of different kinetic equations referring to diffusion, topochemical and other heterogeneous catalytic processes was examined, and it was found that the enzyme process is best described by the modified Prout-Tompkins topochemical equation. According to that kinetic model, the hydrolysis rate depends on the amount of the substrate left and the inhibition of the enzyme by the product formed and, moreover, on the combination of chemical interaction and diffusion processes. There is a compensation effect between activation energy and pre-exponential factor and there are correlations between rate constant, power factor, and wood density. The mechanisms of cellulase hydrolysis of BKP- and SE-treated fast-growing tree species are very similar. The results shows that the structural features of the lignocellulosic material are the controlling factor on the type of the kinetic mechanism. The obtained temperature-time dependence of degree of enzyme hydrolysis is useful for simulation and control of the process.

APA, Harvard, Vancouver, ISO, and other styles

30

McDonald, A. G. "Implications of enzyme kinetics." Biochemical Society Transactions 31, no. 3 (June 1, 2003): 719–22. http://dx.doi.org/10.1042/bst0310719.

Full text

Abstract:

Of the many examples of oscillatory kinetic behaviour known, several are briefly reviewed, including those of glycolysis, the peroxidase–oxidase reaction and oscillations in cellular calcium concentration. It is shown that simple mathematical models employing allosteric rate laws are sufficient to explain the instability of the steady state and the appearance of sustained oscillations. The cAMP-signalling systems of cellular slime moulds and the dynamics of intracellular calcium oscillations illustrate the importance of such oscillophores to inter- and intra-cellular communication and differentiation.

APA, Harvard, Vancouver, ISO, and other styles

31

HAPPEL, JOHN, and PETER H. SELLERS. "ENZYME MECHANISM AND KINETICS*." Chemical Engineering Communications 152-153, no. 1 (October 1996): 433–68. http://dx.doi.org/10.1080/00986449608936577.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Alberty, Robert A. "Rapid-Equilibrium Enzyme Kinetics." Journal of Chemical Education 85, no. 8 (August 2008): 1136. http://dx.doi.org/10.1021/ed085p1136.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Selwyn, MJ. "Fundamentals of enzyme kinetics." Biochemical Education 24, no. 1 (January 1996): 63. http://dx.doi.org/10.1016/s0307-4412(96)80014-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

DAGANI, RON. "STRAIGHTENING OUT ENZYME KINETICS." Chemical & Engineering News Archive 81, no. 24 (June 16, 2003): 26. http://dx.doi.org/10.1021/cen-v081n024.p026.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Byerley, Jennifer, Jin Zhou, and Aaron Teitelbaum. "UGT1A8: Atypical enzyme kinetics." Drug Metabolism and Pharmacokinetics 33, no. 1 (January 2018): S54. http://dx.doi.org/10.1016/j.dmpk.2017.11.185.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Maxwell, A. "In focus: Enzyme kinetics." FEBS Letters 238, no. 1 (September 26, 1988): 217–18. http://dx.doi.org/10.1016/0014-5793(88)80262-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Zimmerman, James. "Enzyme kinetics and mechanism." Biochemistry and Molecular Biology Education 35, no. 5 (2007): 387. http://dx.doi.org/10.1002/bmb.88.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Goel, Rajeev, Takashi Mino, Hiroyasu Satoh, and Tomonori Matsuo. "Comparison of hydrolytic enzyme systems in pure culture and activated sludge under different electron acceptor conditions." Water Science and Technology 37, no. 4-5 (February 1, 1998): 335–43. http://dx.doi.org/10.2166/wst.1998.0659.

Full text

Abstract:

Enzymatic hydrolysis under different electron acceptor conditions in nutrient removal activated sludge treatment processes is a weak link in the Activated Sludge Model no. 2 (Henze et al., 1995). An experimental study was undertaken to gain insight into the hydrolysis process with specific focus on hydrolysis kinetics and rates under different electron acceptor conditions. Two pure cultures, Bacillus amyloliquefaciens (Gram positive) and Pseudomonas saccharophila (Gram negative) were chosen for the study. In addition, activated sludge grown in an anaerobic-aerobic system was tested for enzymatic activity using starch as the model substrate. The hydrolytic enzymes were found to be released into the bulk in pure cultures whereas the enzyme activity was found to be mainly associated with the cell surfaces in activated sludge. Further, it was observed that the development of the hydrolytic enzyme system in Bacillus amyloliquefaciens and P. saccharophila is strongly suppressed under anoxic and anaerobic conditions. However, the effect of anaerobic and aerobic incubation on hydrolytic enzyme activity in activated sludge was found to be small. Starch hydrolysis kinetic data from batch experiments with activated sludge followed substrate saturation kinetics that were linear with biomass concentration. Finally, the similar hydrolytic enzyme activities observed under anaerobic and aerobic phases of a sequencing batch reactor are explained by considering the aspects of enzyme location and enzyme system development under aerobic and anaerobic phases. It is proposed that the floc bound enzymes are recycled in a single sludge system so that an equilibrium exists between enzyme loss and synthesis at steady state.

APA, Harvard, Vancouver, ISO, and other styles

39

Rodriguez, Jon-Marc G., and Marcy H. Towns. "Analysis of student reasoning about Michaelis–Menten enzyme kinetics: mixed conceptions of enzyme inhibition." Chemistry Education Research and Practice 20, no. 2 (2019): 428–42. http://dx.doi.org/10.1039/c8rp00276b.

Full text

Abstract:

Student understanding regarding topics in upper-division courses, such as biochemistry, is not well represented in the literature. Herein we describe a study that investigated students’ reasoning about Michaelis–Menten enzyme kinetics and enzyme inhibition. Our qualitative study involved semistructured interviews with fourteen second-year students enrolled in an introductory biochemistry course. During the interviews students were provided an enzyme kinetics graph, which they were prompted to describe. Students were asked to look for patterns and trends in the data and interpret the graph to draw conclusions regarding the types of enzyme inhibition observed, providing the opportunity for the students to engage in the science practiceanalyzing and interpreting data. Findings indicate students were able to attend to the relevant parameters (V_maxandK_m) in the graph and subsequently associate changes inV_maxandK_mto different types of enzyme inhibitors. However, students expressed difficulty explaining why a specific type of inhibition caused the observed change in the kinetic parameters and there was confusion regarding the distinction between noncompetitive and uncompetitive inhibition. Based on our results, we suggest instruction on enzyme kinetics should emphasize qualitative descriptions of the particulate-level mechanisms related to competitive and noncompetitive inhibition, with less emphasis on discussions of uncompetitive and mixed inhibition in introductory biochemistry courses.

APA, Harvard, Vancouver, ISO, and other styles

40

Kazura, Evan, Ray Mernaugh, and Franz Baudenbacher. "A Capillary-Perfused, Nanocalorimeter Platform for Thermometric Enzyme-Linked Immunosorbent Assay with Femtomole Sensitivity." Biosensors 10, no. 6 (June 24, 2020): 71. http://dx.doi.org/10.3390/bios10060071.

Full text

Abstract:

Enzyme-catalyzed chemical reactions produce heat. We developed an enclosed, capillary-perfused nanocalorimeter platform for thermometric enzyme-linked immunosorbent assay (TELISA). We used catalase as enzymes to model the thermal characteristics of the micromachined calorimeter. Model-assisted signal analysis was used to calibrate the nanocalorimeter and to determine reagent diffusion, enzyme kinetics, and enzyme concentration. The model-simulated signal closely followed the experimental signal after selecting for the enzyme turnover rate (kcat) and the inactivation factor (InF), using a known label enzyme amount (Ea). Over four discrete runs (n = 4), the minimized model root mean square error (RMSE) returned 1.80 ± 0.54 fmol for the 1.5 fmol experiments, and 1.04 ± 0.37 fmol for the 1 fmol experiments. Determination of enzyme parameters through calibration is a necessary step to track changing enzyme kinetic characteristics and improves on previous methods to determine label enzyme amounts on the calorimeter platform. The results obtained using model-system signal analysis for calibration led to significantly improved nanocalorimeter platform performance.

APA, Harvard, Vancouver, ISO, and other styles

41

Ovádi, J., P. Tompa, B. Vértessy, F. Orosz, T. Keleti, and G. R. Welch. "Transient-time analysis of substrate-channelling in interacting enzyme systems." Biochemical Journal 257, no. 1 (January 1, 1989): 187–90. http://dx.doi.org/10.1042/bj2570187.

Full text

Abstract:

The kinetics of dynamically interacting enzyme systems is examined, in the light of increasing evidence attesting to the widespread occurrence of this mode of organization in vivo. The transient time, a key phenomenological parameter for the coupled reaction, is expressed as a function of the lifetime of the intermediate substrate. The relationships between the transient time and the pseudo-first-order rate constants for the coupled reaction by the complexed and uncomplexed enzyme species are indicative of the mechanism of intermediate transfer (‘channelling’). In a dynamically interacting enzyme system these kinetic parameters are composite functions of those for the processes catalysed by the complex and by the separated enzymes. The mathematical paradigm can be extended to a linear sequence of N coupled reactions catalysed by dynamically (pair-wise) interacting enzymes.

APA, Harvard, Vancouver, ISO, and other styles

42

Klinman, Judith P., and Amnon Kohen. "Evolutionary Aspects of Enzyme Dynamics." Journal of Biological Chemistry 289, no. 44 (September 10, 2014): 30205–12. http://dx.doi.org/10.1074/jbc.r114.565515.

Full text

Abstract:

The role of evolutionary pressure on the chemical step catalyzed by enzymes is somewhat enigmatic, in part because chemistry is not rate-limiting for many optimized systems. Herein, we present studies that examine various aspects of the evolutionary relationship between protein dynamics and the chemical step in two paradigmatic enzyme families, dihydrofolate reductases and alcohol dehydrogenases. Molecular details of both convergent and divergent evolution are beginning to emerge. The findings suggest that protein dynamics across an entire enzyme can play a role in adaptation to differing physiological conditions. The growing tool kit of kinetics, kinetic isotope effects, molecular biology, biophysics, and bioinformatics provides means to link evolutionary changes in structure-dynamics function to the vibrational and conformational states of each protein.

APA, Harvard, Vancouver, ISO, and other styles

43

WU, Jia-Wei, and Zhi-Xin WANG. "Activation mechanism and modification kinetics of Chinese hamster dihydrofolate reductase by p-chloromercuribenzoate." Biochemical Journal 335, no. 1 (October 1, 1998): 181–89. http://dx.doi.org/10.1042/bj3350181.

Full text

Abstract:

Substrate effects on the activation kinetics of Chinese hamster dihydrofolate reductase by p-chloromercuribenzoate (pCMB) have been studied. On the basis of the kinetic equation of substrate reaction in the presence of pCMB, all modification kinetic constants for the free enzyme and enzyme–substrate binary and ternary complexes have been determined. The results of the present study indicate that the modification of Chinese hamster dihydrofolate reductase by pCMB shows single-phase kinetics, and that changes in the enzyme activity and tertiary structure proceed simultaneously during the modification process. Both substrates, NADPH and 7,8-dihydrofolate, protect dihydrofolate reductase against modification by pCMB. In the presence of a saturating concentration of NADPH, the value of kcat for 7,8-dihydrofolate in the enzyme-catalysed reaction increased four-fold on modification of Cys-6, accompanied by a two-fold increase in Km for the modified enzyme. The utilization of the binding energy of a group to increase kcat rather than reduce Km implies that the full binding energy of the group is not realized in the formation of the enzyme–substrate complex, but is used to stabilize the enzyme–transition-state complex.

APA, Harvard, Vancouver, ISO, and other styles

44

Brooks, S. P. J. "Equilibrium enzymes in metabolic pathways." Biochemistry and Cell Biology 74, no. 3 (May 1, 1996): 411–16. http://dx.doi.org/10.1139/o96-044.

Full text

Abstract:

It is commonly believed that certain reactions in a metabolic sequence may be at or close to equilibrium because of the large excess of catalytic capacity compared to the flux through these enzyme loci. Simple algebraic manipulations can show that the equilibrium and steady state conditions are mutually exclusive. However, solution of the complete reaction schemes for model "equilibrium" reactions shows that they can remain far from equilibrium even though the ratio of enzyme flux to steady state flux through the overall pathway is high. These calculations show that a reaction's proximity to equilibrium depends on the overall flux through the enzyme locus as well as on the kinetic parameters of the other enzymes in the pathway. Thus, combinations of kinetic parameters may exist that allow certain reactions to approach equilibrium but these conditions are not universal.Key words: equilibria, theoretical kinetics, metabolic control.

APA, Harvard, Vancouver, ISO, and other styles

45

Hochendoner, Philip, Curtis Ogle, and William H. Mather. "A queueing approach to multi-site enzyme kinetics." Interface Focus 4, no. 3 (June 6, 2014): 20130077. http://dx.doi.org/10.1098/rsfs.2013.0077.

Full text

Abstract:

Multi-site enzymes, defined as where multiple substrate molecules can bind simultaneously to the same enzyme molecule, play a key role in a number of biological networks, with the Escherichia coli protease ClpXP a well-studied example. These enzymes can form a low latency ‘waiting line’ of substrate to the enzyme's catalytic core, such that the enzyme molecule can continue to collect substrate even when the catalytic core is occupied. To understand multi-site enzyme kinetics, we study a discrete stochastic model that includes a single catalytic core fed by a fixed number of substrate binding sites. A natural queueing systems analogy is found to provide substantial insight into the dynamics of the model. From this, we derive exact results for the probability distribution of the enzyme configuration and for the distribution of substrate departure times in the case of identical but distinguishable classes of substrate molecules. Comments are also provided for the case when different classes of substrate molecules are not processed identically.

APA, Harvard, Vancouver, ISO, and other styles

46

Coggins, Si'Ana A., Bijan Mahboubi, Raymond F. Schinazi, and Baek Kim. "Mechanistic cross-talk between DNA/RNA polymerase enzyme kinetics and nucleotide substrate availability in cells: Implications for polymerase inhibitor discovery." Journal of Biological Chemistry 295, no. 39 (July 31, 2020): 13432–43. http://dx.doi.org/10.1074/jbc.rev120.013746.

Full text

Abstract:

Enzyme kinetic analysis reveals a dynamic relationship between enzymes and their substrates. Overall enzyme activity can be controlled by both protein expression and various cellular regulatory systems. Interestingly, the availability and concentrations of intracellular substrates can constantly change, depending on conditions and cell types. Here, we review previously reported enzyme kinetic parameters of cellular and viral DNA and RNA polymerases with respect to cellular levels of their nucleotide substrates. This broad perspective exposes a remarkable co-evolution scenario of DNA polymerase enzyme kinetics with dNTP levels that can vastly change, depending on cell proliferation profiles. Similarly, RNA polymerases display much higher Km values than DNA polymerases, possibly due to millimolar range rNTP concentrations found in cells (compared with micromolar range dNTP levels). Polymerases are commonly targeted by nucleotide analog inhibitors for the treatments of various human diseases, such as cancers and viral pathogens. Because these inhibitors compete against natural cellular nucleotides, the efficacy of each inhibitor can be affected by varying cellular nucleotide levels in their target cells. Overall, both kinetic discrepancy between DNA and RNA polymerases and cellular concentration discrepancy between dNTPs and rNTPs present pharmacological and mechanistic considerations for therapeutic discovery.

APA, Harvard, Vancouver, ISO, and other styles

47

Purich, Daniel L. "Enzyme kinetics: From diastase to multi-enzyme systems." Chemistry & Biology 2, no. 7 (July 1995): 449–50. http://dx.doi.org/10.1016/1074-5521(95)90261-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Kulys, J., K. Kriaučiūnas, and R. Vidžiūnaitė. "Kinetic Model of Biphasic Character of Catalyse Inhibition." Nonlinear Analysis: Modelling and Control 8, no. 1 (January 25, 2003): 55–60. http://dx.doi.org/10.15388/na.2003.8.1.15177.

Full text

Abstract:

A mathematical model of kinetics of fungal catalase inhibition with hydroxylamine in presence of substrate (hydrogen peroxide) has been developed. The scheme includes an intermediate formation and slow reversible native enzyme production. The model is based on differential equations of nonstationary kinetics of the enzyme action. The computer simulation was carried out using adaptive Runge-Kuta method. Good satisfactory is achieved if the kinetic constants calculated by modeling nonstationary state of hydrogen peroxide decomposition are used for calculations of inhibition of the catalases at the second phase of inhibition and for kinetics of the intermediate formation, that was determined with stop-flow spectrophotometer.

APA, Harvard, Vancouver, ISO, and other styles

49

Markham, J., T. J. McCarthy, M. J. Welch, and D. P. Schuster. "In vivo measurements of pulmonary angiotensin-converting enzyme kinetics. I. Theory and error analysis." Journal of Applied Physiology 78, no. 3 (March 1, 1995): 1158–68. http://dx.doi.org/10.1152/jappl.1995.78.3.1158.

Full text

Abstract:

We developed a procedure for measuring pulmonary angiotensin-converting enzyme kinetics with fluorine-18 fluorocaptopril and positron emission tomography (PET). The method is based on the application of a compartmental receptor model that represents the kinetics of two species of ligand, presumably the trans and cis conformers of captopril. The input function was characterized and includes corrections for the labeled metabolites of fluorocaptopril. Application of the procedure to lung time-activity data obtained with PET produced estimates of kinetic parameters demonstrating fast kinetics for one conformer and slower kinetics for the other. Simulation studies were performed to evaluate the sensitivity of the estimated parameters to errors in the model assumptions and in measured values for variables required for analysis of the PET data. Estimates for two of the kinetic parameters, the amount of perfused unbound functional enzyme normalized to regional lung volume and the association rate constant for the trans conformer, were relatively stable even with large errors in the input data, varying < 30% from true values for all perturbations. Thus, the procedure produces reliable estimates of the kinetics of the trans conformer of captopril as well as theoretical curves that are close to the observed data.

APA, Harvard, Vancouver, ISO, and other styles

50

Breger, Joyce, Scott Walper, Mario Ancona, Michael Stewart, Eunkeu Oh, Kimihiro Susumu, and Igor Medintz. "Understanding the Enhanced Kinetics of Enzyme-Quantum Dot Constructs." MRS Advances 1, no. 57 (December 28, 2015): 3831–36. http://dx.doi.org/10.1557/adv.2015.35.

Full text

Abstract:

ABSTRACTBio-inspired, hybrid architectures employing quantum dots (QDs) appended with functionally active biomolecules such as enzymes have the potential to be utilized in numerous applications. Some examples include nanosensors for medical diagnostics, chemical/biological threat detection, as well as “bio-factories” in complex industrial synthetic processes. The main advantage in creating these nanofactories is increased rates in catalysis and efficiency when enzymes are associated with nanoscaffolds, as shown in numerous studies. However, the mechanism for this enhancement remains elusive. Gaining a fundamental, mechanistic understanding of enzyme-QD nanostructures is important in the development of numerous device applications. In this work, we review an array of enzymes attached to QDs and generate a hypothesis in regards to the unique architecture of the enzyme-nanoparticle (NP) construct that leads to increases in catalysis. We highlight work with phosphotiresterase (PTE) attached to two distinctly sized QDs in neutralizing a simulant nerve agent, as well as in other enzyme systems.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Enzyme kinetics'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles