The effect of pH variations on the activities of C-esterase

Abstract

Purified C esterase (from hog''s kidney) is stable within the range pH 5.6-10.2. After exposure of the enzyme to these extremes of pH, its activity can be fully recovered by readjustments of the pH to 8.0. The activating effect of organic mercurials is pH-dependent. The changes are immediate and completely reversible. Some of the preparations of C-esterase appear to contain a dialyzable cofactor, which is lost rapidly by exposure of the preparations to pH 5.6 or to pH 10.2. The pH-activity curves for phenyl acetate and its p-methoxy derivative exhibit an optimum around pH 8. In this respect, C-esterase behaves similarly to esterases of the A- and B-type. In contrast, the rate of the enzymic hydrolysis of p-nitrophenyl acetate increases steadily up to the experimental limit of pH 9.5.