Kinetics and Mechanisms of Action

Kinetics and Mechanisms of Action.—A book entitled Kinetics of Enzyme Mechanisms has examined the wide-ranging concepts and methods that are used to obtain information on enzyme mechanisms. It covers the essential ideas behind various kinetic methods, with little mathematical detail, and includes sections on inhibitors, activators, co-operative interactions, and transport across membranes. 

A general method for the detailed study of enzymic reactions considers the complete enzyme-substrate complex and the surrounding solvent, and evaluates all the quantum-mechanical and classical energy factors that can affect the reaction pathway.  

A non-mathematical, steady-state approach to enzyme kinetics has been 

Functions.—The clearance of glycoside hydrolases from the circulatory system of rats has been examined. 

The first volume of a new series entitled Applied Biochemistry and Bioengineering deals with the principles of immobilized enzymes, which, among other topics, are also discussed in one of the latest volumes of Methods in Enzymology . Recent reviews have covered the uses of immobilized enzymes and immobilized microbial cells in industry, the design of immobilized-enzyme flow reactors, the properties of immobilized enzymes, the reactions used to immobilize enzymes, and the uses of immobilized enzymes in clinical diagnosis, detoxification, and therapy, etc. and of immobilized microbial cells. 

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Methods for Reducing Toxic Effects. Limited information is available on treatments to alleviate the symptoms of tetryl exposure. These include treatment of the dermatitis with calamine lotion and/or zinc oxide preparations, treatment of dermatitis and ocular irritation with aluminum acetate or boric acid compresses, and treatment of hypersensitivity-like symptoms (including severe dermatitis and asthma-like symptoms) with epinephrine or antihistamines (Bain and Thomson I 954 Bergman 1952 Cripps 1917 Eddy 1943 Ruxton 1917 Smith 1916 Troup 1946 Witkowski et al. 1942). The data on the pharmacokinetics of tetryl are also limited (Zambrano and Mandovano 1956). In order to develop mitigating agents, further studies are needed on its kinetics and mechanisms of action. 

An improved approach to enzyme-catalysed peptide synthesis stems from a thorough understanding of the kinetics and mechanism of action of proteinases. Many proteinases function by the Ping Pong Bi Bi mechanism (Roberts, 1977) and hydrolysis of an V-protected amino acid or peptide ester involves the acylation of a Ser or Cys side-chain by the ester with the liberation of the relevant alcohol or amino component and the formation of a covalent O- or S-acylated enzyme. The latter is hydrolysed in a second step ... 

Craig N K Merck 9 Garrett ER, Heman-Ackah SM and Perry GL, Kinetics and mechanisms of action of drugs on microorganisms XI,... 

KINETICS AND MECHANISMS OF AGONIST ACTION (a) Ion channel receptors... 

The use of enzymes and whole cells as catalysts in organic chemistry is described. Emphasis is put on the chemical reactions and the importance of providing enantiopure synthons. In particular kinetics of resolution is in focus. Among the topics covered are enzyme classification, structure and mechanism of action of enzymes. Examples are given on the use of hydrolytic enzymes such as esterases, proteases, lipases, epoxide hydrolases, acylases and amidases both in aqueous and low-water media. Reductions and oxidations are treated both using whole cells and pure enzymes. Moreover, use of enzymes in sngar chemistiy and to prodnce amino acids and peptides are discnssed. 

D and E appear to stimulate the formation of 0 directly. The ability of A 23187 to elicit formation of O from PMNs 24,59,60,68.70) appears to be due to its action as an ionophore for Ca (see below). Other active stimuli include fluoride, notable because its effect is reversible human leucocyte pyrogen which might have a function in vivo and phorbol myristate acetate The latter has been very useful as a potent stimulus of the burst in various studies of the kinetics and mechanism of activation of the burst. 

Our laboratory has been studying the kinetics (1) and mechanism of action (2) of phospholipase A2 which catalyzes the hydrolysis of the fatty acyl chain in the sn-2 position of phospholipids to give the 1-acyl lyso-phospholipid product ... 

The kinetics and mechanisms of the majority of these reactions were also studied. It is shown that successful application of hydrogen peroxide is promoted by a combination of high induction properties and effectiveness and specificity of action in it, accompanied by the harmlessness of hydrogen peroxide dissociation products. 

Many enzymes catalyze reactions with two interacting substrates, and although the kinetics of these reactions are more complex than those of one-substrate reactions, they still obey Michaelis-Menten kinetics. Reactions of the type A + B <= P + Q usually fall within either of two classes with respect to kinetic behavior and mechanism of action. 

The following actions are devoted to a discussion of the most relevant publications dealing with the kinetics and mechanism of initiation processes proceeding throu water cocatalj is. 

V.N. Kondratiev and E.E. Nikitin, Kinetics and Mechanisms of Gas-Phase Re actions.Moscovi, Nauka, 1974, 558p. (in Russian). 

The kinetic stoicheiometry and mechanism of action of electrogenerated bromine with furan, pyrrole, and thiophen have been studied in detail/ Electrochemical trifluoromethylation of 2,5-dihydrothiophen 1,1-dioxide has been carried out/ ... 

U.sing this method, Yuksel et al. (112) prepared a. system for the pH-depen-dem controlled release of nicarpidine hydrochloride. Kim et al. (114) demonstrated that treatment of hyperteasion with nifedipine using Eudragit (and other polymers) nanoparticles provided controlled release methods, with prolonged action and low initial burst. The kinetics and mechanism of nifedipine release by Eudragit particles have been analyzed by Chowdaiy and Sankar (IIS). 

This reaction has been studied by anumber of authors [13-15], But the conclusions in most cases differ from one another, perhaps because of differences and complicated contents of formed products. Special interest is pointed out on the action of ozone as an initiator in the oxidation processes [16-18], modifying polymer agent [19-21], oxidizer at the preparation of alcohols, ketones, etc. [22-24]. The kinetics and mechanism of this reaction have been intensively discussed [25—46]. The main goal of our present paper is dedicated to the fundamental problems of the kinetic and mechanism of these reactions [47-64]. 

Enzymes that hydrolyze proteins and other compounds composed of amino acids were among the first biological catalysts to be discovered, and they have continued to be prominent in studies of enzyme structure, kinetics, activation, and mechanism of action. The crystallization of the enzyme urease by Sumner was followed by the crystallization of various proteolytic enzymes in the laboratory of Northrop. These studies established that catalytic activity is associated with what appear to be pure proteins all well-defined enzymes isolated subsequently have also proved to be proteins, although many contain additional components. The study of enzymatic reactions involving proteins as substrate, therefore, gives insight into the chemical nature of enzymes as well as the mechanisms by which they act. 

New data on the specificity and mechanism of action of porcine pepsin are presented, including statistical analysis of protein cleavage by the enzyme, kinetics of synthetic substrates, enzyme inhibition and activation, kinetics of transpeptidation reaction, and 0 exchange studies. 

Properties and Reactions.—Physicochemical studies of axial ligation of pyridine to cobalt corroles have been carried out/ and the kinetics and mechanism of cobalt-carbon bond cleavage in the alkylation of tin and mercury ions have also been studied. The mechanism of action of the vitamin coenzyme has been reviewed/ and several studies of the mechanism of cobalt-carbon bond cleavage and isomerization reactions of the model cobalt cobaloxime system have been published. ... 

Over the past ten years there have been many papers published about mammalian sialidase and a few about avian sialidase. Organellar and subcellular distribution studies have been reported upon, as have substrate specificity, purification, physical properties and possible effects of enzyme action. Much of the work is suggestive but not complete, i.e., characterization of the physical properties such as the kinetic parameters, and Vmaxj has only been done on crude enzyme preparations. Composition, molecular weight, and mechanism of action are not known. 

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