Chapter 7 - Factors Influencing Enzyme Activity

Abstract

This chapter focuses on the chemical and physical factors as well as the kinetic approaches used to characterize their impact on catalysis, with the exception of inhibitor effects and regulatory effects. Also considered here are the kinetic behavior of crystalline enzymes, kinetic proofreading, as well as the effects of site-directed mutation on enzyme structure, stability, and catalysis. Enzyme catalysis is influenced by many chemical and physical factors. Among the former are low-molecular-weight substances (e.g., protons, metals and other inorganic ions, buffer ions, various organic molecules, as well as natural and synthetic enzyme activators, inhibitors, and stabilizers) and macromolecular components (e.g., proteins, polysaccharides, biomembranes, and other polyelectrolytes). Physical factors include temperature, pressure, ionic strength, solvent polarity, immobilization, substrate sequestration, and molecular crowding. The chemical and structural complexity of enzymes, as well as their interactions, explains why an enzyme's activity can be affected in both subtle and substantial ways. In some cases, an enzyme's entire structure is altered; in other circumstances, the effect is manifestly local. In others the effects are exerted by binding at distal sites that rely on flexibility within the protein's architecture to communicate binding site occupancy to the catalytic center.