Mechanistic Interpretation of Empirical Enzyme Rate Equations

Abstract

THE kinetic behaviour of most enzymes is more complicated than that described by Michaelis and Menten¹ for the relatively simple mechanism: E + S = ES→E + P. Many enzymes have more than one substrate or product; others are inhibited by product and/or substrate, and their rate equations are correspondingly complex. For such enzymes, Michaelis–Menten kinetics are sometimes applicable at limiting conditions (such as velocities measured in the absence of product—that is, in zero time—using a large excess of all but one substrate), but this normally precludes any rigorous interpretation of the results. Oversimplifications of this kind have resulted in conflicting interpretations of the same data, leading to unnecessary controversy.