Microbiology Procedure

Index >> Enzymes,Isozymes and Coenzymes >> Control of Enzyme Action

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Enzymes,Isozymes and Coenzymes Nomenclature of Enzymes Oxidoreductases Transferases HydSrolases Lyases Isomerases Ligase - Synthetases Enzymes and their Functions Structure of Enzymes Active Site of Enzymes Specificity of Enzymes Activation Energy of Enzymes Effect of Temperature on Enzyme Activity

Control of Enzyme Action

	Control of Enzyme Action - The action of an enzyme can be controlled by its product (feed back). Accumulation of the product slows down the rate of chemical reaction. There is, however, a more complicated system of control in linked systems. Many reactions in the cell take place in a series of steps, each step being controlled by a separate enzyme.
The substrate S1 gives rise to the product S2 through a reaction controlled by the enzyme E1. S2 now becomes the substrate of another reaction controlled by the enzyme E2, and so on. In the synthesis of different amino acids from aspartate, lysine is formed after several steps. Aspartate-->Aspartyl phosphate--> Aspartyl semialdehyde-->Lysine
It has been found that the addition of lysine stops the whole chain of reactions. Here inhibition is produced not in the last step of the series, but in the first step. Thus lysine affects the action of an enzyme which is producing an entirely different substance. This has been explained by suggesting that the enzyme has a 'control site' in addition to the 'active site' . When the control site is occupied by a control substance (lysine, in this case), the latter distorts the shape of the enzyme
One or more reactive amino acids are removed from the active site, which is thus rendered nonfunctional. Enzymes which undergo this type of behaviour are called allosteric enzymes. They control an entire series of reaction through the end product.

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Effect of Enzyme Concentration Inhibition of Enzymes Control of Enzyme Action ISOZYMES COENZYMES - COFACTORS Coenzymes and their Vitamin Precursors

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