INFLUENCE OF ENZYME ACTIVATORS AND INHIBITORS, PRESENT IN AN ENZYME PREPARATION, ON RELATIONS BETWEEN REACTION RATE AND ENZYME CONCENTRATION

The relation between the rate of enzymic reaction and the concentration of enzyme (v vs. e relation) is theoretically discussed with enzyme preparations contaminated with an effector, which inhibits or activates the reaction. The v vs. e relation is expressed by a part of a hyperbola or parabola that is experimentally obtainable; the molar ratio of an effector to the enzyme (R) is responsible for shape of the curve. The shape is a parabola at R = 1, and a hyperbola at R ≠ 1. With increasing concentrations of the enzyme, the slope of a curve representing v vs. e relation decreases in the presence of inhibitors, whereas it increases in the presence of activators. Either activators or inhibitors may be classified into two types, one capable of combining with the free enzyme and the other with the substrate-enzyme complex. Both types of effector influence the shape of the v vs. e curve in a similar manner, but they are distinguishable by evaluating the effect of substrate concentration on the v vs. e relation. © 1969 Academic Press Inc. (London) Ltd.