Academic literature on the topic '-1,3-glucanase, Enzyme kinetics'

Unlike other group transfer reactions in biochemistry, the actions of nitrogen transferring enzymes do not follow a single unifying chemical principle. Nitrogen-transferring enzymes catalyze aminotransfer, amidotransfer, and amidinotransfer. An aminotransferase catalyzes the transfer of the NH2 group from a primary amine to a ketone or aldehyde. An amidotransferase catalyzes the transfer of the anide-NH2 group from glutamine to another group. These reactions proceed by polar reaction mechanisms. Aminomutases catalyze 1,2-intramolecular aminotransfer, in which an amino group is inserted into an adjacent C—H bond. The action of lysine 2,3-aminomutase, described in chapter 7, is an example of an aminomutase that functions by a radical reaction mechanism. Tyrosine 2,3-aminomutase also catalyzes the 2,3-amino migration, but it does so by a polar reaction mechanism. In this chapter, we consider NH2-transferring enzymes that function by polar reaction mechanisms. Transaminases or aminotransferases are the most extensively studied pyridoxal-5'-phosphate (PLP)–dependent enzymes, and many aminotransferases catalyze essential steps in catabolic and anabolic metabolism. In the classic transaminase reaction, aspartate aminotransferase (AAT) catalyzes the fully reversible reaction of L-aspartate with α-ketoglutarate according to fig. 13-1 to form oxaloacetate and L-glutamate. Like all aminotransferases, AAT is PLP dependent, and PLP functions in its classic role of providing a reactive carbonyl group to function in facilitating the cleavage of the α-H of aspartate and the departure of the α-amino group of aspartate for transfer to α-ketoglutarate (Snell, 1962). PLP in the holoenzyme functions in essence to stabilize the α-carbanions of L-aspartate or L-glutamate, the major biological role of PLP discussed in chapter 3. The functional groups of the enzyme catalyze steps in the mechanism, such as the 1,3-prototropic shift of the α-proton to C4' of pyridoxamine 5'-phosphate (PMP). The steady-state kinetics corresponds to the ping pong bi bi mechanism shown at the bottom of fig. 13-1. This mechanism allows L-aspartate to react with the internal aldimine, E=PLP in fig. 13-1, to produce an equivalent of oxaloacetate, with conversion of PLP to PMP at the active site (E.PMP), the free, covalently modified enzyme in the ping pong mechanism.

Klavs S. Jensen of MIT showed (Angew. Chem. Int. Ed. 2014, 53, 470) that “batch” kinetics could be developed in flow by online IR analysis and continuous control. Professor Jensen also demonstrated (Org. Process Res. Dev. 2014, 18, 402) the contin­uous flow production of an active pharmaceutical product, the direct renin inhibitor aliskiren, over two steps and two crystallizations, starting from two advanced interme­diates. Michael Werner and Rainer E. Martin of Hoffmann-La Roche AG Basel com­bined (Angew. Chem. Int. Ed. 2014, 53, 1704) flow synthesis with a flow-based bioassay to develop structure–activity relationships for a series of β-secretase inhibitors. Carlos Mateos of Lilly S. A. and C. Oliver Kappe of the University of Graz used (J. Org. Chem. 2014, 79, 223) flow photolysis to promote the bromination of 1 to 2. Alessandro Palmieri of the University of Camerino and Stefano Protti of the University of Pavia added (Adv. Synth. Catal. 2014, 356, 753) the aldehyde 3 to the acceptor 4 to give, after in-flow reduction, the lactone 5. Peter H. Seeberger of the Max Planck Institute Mühlenberg showed (Org. Lett. 2014, 16, 1794) that the tum­bling action of flow photolysis made the production of 7 by the unlinking of 6 from the polymer bead particularly efficient. Enzymes can also be used under flow conditions. Jörg Pietruszka of the Heinrich-Heine-Universität Düsseldorf employed (Adv. Synth. Catal. 2014, 356, 1007) com­mercial laccase to prepare 10 by coupling 8 with 9. Gas–liquid mixing under flow conditions can also be effective. Núria López of ICIQ Catalonia and Javier Pérez-Ramírez of ETH Zurich developed (Chem. Eur J. 2014, 20, 5926) conditions for the selective hydrogenation of an alkyne 11 to the cis alkene 12. Jun-ichi Yoshida of Kyoto University trapped (Chem. Eur J. 2014, 20, 7931) the inter­mediate organolithium from 13 with CO₂ to give a carboxylate that was carried on to the purifiable O-Su ester 14, ready for further coupling. Timothy F. Jamison, also of MIT, prepared (Angew. Chem. Int. Ed. 2014, 53, 3353) the amino phenol 17 by add­ing the chloromagnesium amide from 16 to the intermediate benzyne from 15, then oxidizing the product with air.

Prothrombinase is the multi -component enzyme composed of factor Xa and the cofactor, factor Va, that assemble on a phospholipid surface in the presence of calcium ion. Fluoresence stopped-flow kinetic studies of prothrombinase assembly in the absence of the substrate, prothrombin were undertaken at saturating concentrations of calcium ion, using phospholipid vesicles (PCPS), factor Va and factor Xa modified at the active-site with the fluorophore dansyl-glutamylglycinylarginylchloro methylketone (DEGR-Xa). The substantial fluorescence enhancement of DEGR-Xa in the presence of factor Va, PCPS

Articular cartilage is a specialized avascular connective tissue found at the contact regions of diarthrodial joints. Cartilage has few cells (< 5% of the volume), though these cells can maintain the balance of turnover in healthy tissue, when the tissue is damaged, they are not able to repair the defects [1–3]. Extra cellular matrix (ECM) in cartilage comprises water, collagen (principally type II), proteoglycans and noncollagenous proteins. The type II collagen network, which is the dominant structural protein in cartilage ECM, constrains the expansion of the resident PGs and is generally

"Heparin rebound", the in vivo appearance of measurable heparin anticoagulant activity following theapparent neutralization of heparin by protamine, hasbeen a problem sporadically associated with the use of heparin in cardiovascular surgery. A number of mechanisms have been proposed to explain rebound, and to some extent each may contribute to the phenomena. As yet no reliable, predictable method has been demonstrated for measuring, reproducing or quantifying "heparin rebound".We have demonstrated and measured the appearance of heparin anticoagulant activity following neutralization with prota

A kinetic model, based on published studies of thrombin neutralization, is used to examine factors that limit spread of free thrombin in a simple plasma. It employs equations with presently available rate parameters which describe the courses of the major thrombin-binding reactions at 37°C in buffered saline solutions approximating plasma ultrafiltrate. Thrombin is bound reversibly by fibrinogen and fibrin-1 polymers as enzyme-substrate complexes (1) and by “fibrin” at a non-proteolyt ic site (2), and essentially irreversibly by antithrombins (3). These bindings reduce free thrombin levels and

Plasminogen activator (PAs) are enzymes that convert the zymogen plasminogen into the trypsin-like protease plasmin, which degrades extracellular matrix proteins and fibrin in the course of fibrinolysis, embryogenesis, tissue remodeling and in tumor metastasis. Plasminogen activator inhibitors (PAIs) are important modulators of PA activity. Several proteins have been identified which inhibit at fast rates urokinase (u-PA) and tissue-type PA (t-PA). In the order of inhibition rate constants these are: a) PAI-1, present in human plasma and platelet extracts and purified from human endothelial ce