Biochemistry

Reversible inhibition occurs during the period of direct interaction of the enzyme with the inhibitor, the removal of which again returns the activity to the enzyme. Such inhibition can occur in a competitive and non-competitive manner. Competitive inhibition is possible when the inhibitor contains chemical groups similar to the substrate, i.e., is its structural analogue and is able to interact with the active center of the enzyme. The basis of this type of inhibition is the competition between the substrate and the inhibitor for joining the active group of the enzyme (Fig. 3.7). Such an inhibitor, binding to the enzyme, forms an inhibitor ­ enzyme complex. However, this only happens if the concentration of the inhibitor exceeds the amount of substrate. With increasing substrate concentration, it displaces the inhibitor from the active center of the enzyme, which restores its catalytic function. Thus, the action of competitive inhibitors can be reduced or eliminated by increasing the amount of substrate. Figure 3.7 - Scheme of competitive inhibitor activity At non-competitive inhibition, the inhibitor interacts not with the active substrate center of the enzyme, but with allosteric. As a result, the structure of the enzyme changes, including the active center, to which the substrate can no longer attach. In this case, the concentration of the inhibitor does not matter. Removal of the inhibitor does not always lead to restoration of the properties of the enzyme. Enzyme inhibitors are found in body tissues. A substance of protein nature was found in the pancreas that inhibits trypsin activity. A compound inhibiting pepsin activity is also known. These substances are called antienzymes, their action is reversible. Under certain conditions, antienzymes are cleaved from enzymes that leads to the restoration of the activity of the latter. 88