Asymmetric enzyme kinetics of F_{1}-ATPase induced by rotation-assisted substrate binding

Abstract

We demonstrate asymmetric enzyme kinetics of a biomolecular motor F_{1}-ATPase between synthesis and hydrolysis of adenosine triphosphate (ATP). Our experiments show that ATP hydrolysis follows Michaelis-Menten kinetics, but ATP synthesis, which is an F_{1}-ATPase's primary biological role, deviates from it. Specifically, the synthesis rate is sustained even at low substrate concentrations. Analysis of a theoretical model consistent with the experimental results reveals that ATP synthesis implements a rotation-assisted mechanism, in which a limited binding rate at low substrate concentration is partially compensated for by rotation to an angle where the binding rate is high. The results may imply that F_{1}-ATPase implements a regulatory mechanism of enhancing substrate binding for ATP synthesis.