A Steady-State Approach for inhibition of Heterogeneous Enzyme reactions.

A Steady-State Approach for inhibition of Heterogeneous Enzyme reactions.
Biochem J. 2020 May 11;:
Authors: Kari J, Schiano-di-Cola C, Hansen SF, Badino SF, Sørensen TH, Cavaleiro AM, Borch K, Westh P
Abstract
Kinetic theory of enzymes that modify insoluble substrates is still underdeveloped, despite the prevalence of this type of reaction both in vivo and industrial applications. Here, we present a steady-state kinetic approach to investigate inhibition occurring at the solid-liquid interface. We propose to conduct experiments under enzyme excess (E0>>S0), i.e. the opposite limit compared to the conventional Michaelis-Menten framework. This inverse condition is practical for insoluble substrates and elucidates how the inhibitor reduces enzyme activity through binding to the substrate. We claim that this type of inhibition is common for interfacial enzyme reactions because substrate accessibility is low, and we show that it can be analyzed by experiments and rate equations that are analogous to the conventional approach, except that the roles of enzyme and substrate have been swapped. To illustrate the approach, we investigated the major cellulases from Trichoderma reesei (Cel6A and Cel7A) acting on insoluble cellulose. As model inhibitors, we used catalytically inactive variants of Cel6A and Cel7A. We made so-called inverse Michaelis-Menten curves at different concentrations of inhibitors and found that a new rate equation ac...

Source: The Biochemical Journal - May 10, 2020 Category: Biochemistry Authors: Kari J, Schiano-di-Cola C, Hansen SF, Badino SF, Sørensen TH, Cavaleiro AM, Borch K, Westh P Tags: Biochem J Source Type: research