The theoretical analysis of kinetic behaviour of “hysteretic” allosteric enzymes. I. The kinetic manifestations of slow conformational change of an oligomeric enyzme in the Monod, Wyman and Changeux model

Abstract

The curves of the time ( t) dependent product (Pr) accumulation for Monod, Wyman & Changeux model (1965), where the rate of installation of equilibrium between two conformational states of oligomeric enzyme (R ⇄ T) is comparable to that of enzymatic process, are theoretically analysed. It is assumed that the complexes of R and T forms are in rapid equilibrium with the free components. The character of the effective rate constant of conformational transition R ⇄ T and the value of τ (where τ is the intercept of the linear part of the kinetic curve of [Pr] versus t with the time axis) versus the substrate concentration is analysed. It is also shown that slow conformational transition R ⇄ T can be manifested by an unusual shape for Monod et al. model plots of initial velocity of the enzyme reaction v. the substrate concentration (these curves can clearly display expressed inflection points and Hill's cooperativity coefficient less than unity).