Inhibitors allosteric phenomena

In die metabolic pathway to an amino add several steps are involved. Each step is die result of an enzymatic activity. The key enzymatic activity (usually die first enzyme in the synthesis) is regulated by one of its products (usually die end product, eg die amino add). If die concentration of die amino add is too high die enzymatic activity is decreased by interaction of die inhibitor with the regulatory site of die enzyme (allosteric enzyme). This phenomenon is called feedback inhibition. 

Non-competitive inhibitors. These inhibitors bind to the enzyme or the enzyme-substrate complex at a site other than the active site. This results in a decrease in the maximum rate of reaction, but the substrate can still bind to the enzyme. An analogous concept is that of allosteric inhibition. The site of binding of an allosteric inhibitor is distinct from the substrate binding site. In this case, the inhibitor is not a steric analog of the substrate and instead binds to the allosteric site (the phenomenon was termed thus by Monod and Jacob). 

Some comments are required on effectors which are of importance in metabolic and other regulation phenomena. The term allosteric inhibition was introduced by Monod, Changeux Jacob (1963) to explain the discovery of feedback inhibitors, which are competitive with the substrate but not closely structurally related to it. Such inhibitors were called allosteric in contrast to the usual competitive inhibitors which are isosteric with the substrate to fit competitively into the same binding site. Allosteric competitive inhibition occurs at a site (allosteric site) which is separate from the substrate binding sites. Conununication between these separate sites about respective occupancy occurs through conformation changes and these are transmitted through subunit interfaces. The term was extended to the related control phenomenon of allosteric activation, which occurs when a metabolite binds to an allosteric site and decreases the for... 

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