Interaction of Asp. melleus Semi-Alkaline Protease with Benzeneboronic Acid

Abstract

Benzeneboronic acid (BBA), a possible transition-state analog for serine proteases, was found to inhibit Asp. melleus semi-alkaline protease [EC 3. 4. 21. 15]. The pH dependence of inhibitor constants was studied by the pH-stat method using N-acetyl-L-tyrosine ethyl ester as a sub-strate at 25°C. From the pH dependence of the association constant (reciprocal inhibitor constant), a pK value of 6.6, which may be attributable to the catalytic histidine residue of the enzyme, was estimated. The BBA-enzyme interaction was studied kinetically by the tempera-ture-jump method. Apparent association and dissociation rate constants were determined at pH 6.5.