"Viral" expansion of enzyme flux and use of quasi-chemical approximation for two-state enzymes with enzyme-enzyme interactions.

Abstract

Two examples of enzyme systems with interactions at steady state are treated here. In both cases, the enzyme cycle has 2 states and quasi-equilibrium in spatial distributions obtains at steady state (because f.alpha. + f.beta. = 1). The 1st example is a dilute solution of enzyme molecules in a solvent. Flux (turnover) per molecule is expanded in powers of the enzyme concentration (a "virial" expansion). Aggregation of the enzyme molecules in solution is considered as a special case. In the 2nd example, an arbitrary lattice of enzyme molecules is treated, with nearest-neighbor interactions, using the well-known quasi-chemical approximation. Flux per molecule is obtained. Critical behavior and hysteresis are illustrated.