Substrate Specificity, Mode of Action, and of Inhibition by Organic Acids of Purified Acetylesterase from Sclerotinia Fungus

Abstract

Acetylesterase (AcE) of Sclerotinia libertiana was purified approximately 1170-fold, and proved homogeneous by electrophoresis, ultracentrifugation and chromatography. The purified AcE hydrolyzed various acetyl esters in the following order; vinyl acetate, tri-acetin, n-butyl acetate, p-nitrophenylacetate, diacetin, ethylene glycol diacetate, monoacetin, ethyl acetate, acetylcholine, methyl acetate. It also had apparently a slight activity on tannic acid, benzoylcholine, methyl butyrate and acetic anhydride.The mode of AcE reaction on these substrates could be divided into two types of group by Lineweaver-Burk plot, one forms the enzyme-substrate complex, ES, and the other, SES additionally combining substrate at a high substrate concentration.From the inhibition experiment by organic acids, it was suggested that the neighbouring carboxyl groups of the di-, or tribasic acid such as citric, cis-aconitic, succinic, and maleic acid have a significance on inhibition of the AcE. Also, choline esterase inhibito...