Kinetics of Irreversible Inhibition of Yeast Alcohol Dehydrogenase during Modification by o-Phthaldehyde

Abstract

The kinetic theory of the substrate reaction during irreversible inhibition of enzyme activity described previously has been applied to a study on the kinetics of the course of inactivation of yeast alcohol dehydrogenase (YADH) by o-phthaldehyde (OPTA). The microscopic constants for the reaction of the inactivators with the free enzyme and with the enzyme-substrate complexes were determined. The inactivation is a monophasic pseudo-first-order reaction with OPTA. The apparent rate constant A is independent of the OPTA concentration, indicating that the inactivation is a noncomplexing inhibition. The marked protective effect of substrates on the inactivation of YADH by OPTA has been observed. This result suggests that the modification of the enzyme by OPTA may occur at the active site.

Inhibition effects of furfural on alcohol dehydrogenase, aldehyde dehydrogenase and pyruvate dehydrogenase

“…The catalytic activity tends to decrease with increasing size of the aldehyde substrate. Reversibility of the inactivation is also an issue when the enzyme faces some substrates such as o-phthalaldehyde [26].…”