Mechanisms of Enzyme Action

Action of HP on Microorganisms and Enzymes Mechanisms of Action on Microorganisms... 

The crystallographic studies to 1.6 A resolution of the same enzyme from different sources, in different space groups with different unit cell dimensions, give the same folding of the backbone and the same conformation of most of the conserved side chains. Thus we have found out how nature built this protein. We are still trying to find out how it effects the catalysis. Details of the actual enzymic mechanisms of action of proteins require study of the protein with and without bound ligand [236]. Lesk [5], however, warns us that even if... 

Carbocyclic nucleoside analogues Classification, target enzymes, mechanisms of action and synthesis 12UK729. 

In spite of all our knowledge of the structure of enzymes and the thermodynamics and kinetics of enzyme-catalyzed reactions, we are still far from an adequate understanding of the enzymic mechanism of action. In modem organic chemistry reactions are explained on the basis of the electron theory and the chemical bond. In principle, this explanation should also apply to enzymic transformations, but so far it has been possible only in a few instances to arrive at the detailed reaction mechanism. 

Chelation is a feature of much research on the development and mechanism of action of catalysts. For example, enzyme chemistry is aided by the study of reactions of simpler chelates that are models of enzyme reactions. Certain enzymes, coenzymes, and vitamins possess chelate stmctures that must be involved in the mechanism of their action. The activation of many enzymes by metal ions most likely involves chelation, probably bridging the enzyme and substrate through the metal atom. Enzyme inhibition may often result from the formation by the inhibitor of a chelate with a greater stabiUty constant than that of the substrate or the enzyme for a necessary metal ion. 

Studies on the mechanism of action of /3-lactam antibiotics have shed considerable light on how these agents kill bacteria. They also help explain qualitative differences between various agents and why there is a correlation between the reactivity of the /3-lactam and antibacterial activity. However, it is also clear that reactivity is only one factor in determining how effectively a given /3-lactam antibiotic will inactivate bacterial enzymes (82BJ(203)223). 

Boyer, P. D., 1970. The Enzymes, 3rd ed. New York Academic Pre.s.s. A good reference. source for the mechanisms of action of vitamins and coenzymes. 

Chang, S. I., and Hamme.s, G. G., 1990. Structure and mechanism of action of a mnltifnnctional enzyme Fatty acid. syndia.se. Accounts of Chemical Research 23 363—369. 

The metabolic breakdown of triacylglycerols begins with their hydrolysis to yield glycerol plus fatty acids. The reaction is catalyzed by a lipase, whose mechanism of action is shown in Figure 29.2. The active site of the enzyme contains a catalytic triad of aspartic acid, histidine, and serine residues, which act cooperatively to provide the necessary acid and base catalysis for the individual steps. Hydrolysis is accomplished by two sequential nucleophilic acyl substitution reactions, one that covalently binds an acyl group to the side chain -OH of a serine residue on the enzyme and a second that frees the fatty acid from the enzyme. 

Figure 29.2 MECHANISM Mechanism of action of lipase. The active site of the enzyme contains a catalytic triad of aspartic acid, histidine, and serine, which react cooperatively to carry out two nucleophilic acyl substitution reactions. Individual steps are explained in the text.

According to their genetic relationship and their biochemical mechanism of action (3-lactamases are divided into enzymes of the serine-protease type containing an active-site serine (molecular class A, C, and D enzymes) and those of the metallo-protease type (molecular class B enzymes), which contain a complex bound zinc ion. 

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