# A test for measuring the effects of enzyme inactivation

### Abstract

In the single-enzyme, single-substrate reaction with non-mechanism-based enzyme inactivation, the formation of the product and inactivation of the enzyme occur independently. For this reaction, we show that the steady-state hypothesis is applicable even when degradation of the enzyme occurs. An equation for the rate of product formation has been derived and it shows Michaelis-Menten kinetics with an apparent Michaelis-Menten constant $K_M^{app}$ = $K_M$ + $K_δ$ where $K_δ$ is the enzyme inactivation constant. Use of a Lineweaver-Burk plot yields values for $K_M^{app}$, which can be used to estimate $K_δ$ and, consequently, the degree of enzyme inactivation in a particular experiment. We employ this methodology to estimate the inactivation constant for the arsenate reductase catalyzed production of arsenite with appreciable enzyme inactivation. (c) 2006 Elsevier B.V. All rights reserved.

Publication
BIOPHYSICAL CHEMISTRY 125, 269-274