Abstract
The major amylolytic enzyme from Hypocrea peltata was purified by consecutive column chromatography procedure, and characterized as a glucoamylase [EC 3.2.1.3]. The specific activity was brought to 26.8 units of soluble starch-saccharifying activity per mg of enzyme protein, and the enzyme was homogeneous on polyacrylamide gel disc electrophoresis. The molecular weight of the enzyme was estimated to be about 73, 000 by SDS polyacrylamide gel electrophoresis. The optimum pH and temperature of the enzyme were pH 4.5-5.0 and 60°C, respectively. The enzyme was stable over the range of pH 4.0-7.0 at 4°C for 24 hr, and was completely inactivated by heating at 80°C for 10 min. The enzyme was completely inactivated by 1 mM Hg2, and partially by 1 mM Ag+ and Fe2+. The action of the enzyme on glycogen, amylopectin, amylose, soluble starch, short chain amylose (DP=17.3), maltose, isomaltose and panose was studied. Glucose was the sole hydrolysis product found in digests of these substrates. The α-configuration of the anomeric carbon atoms is produced in the hydrolysis products of soluble starch. The Km and Vmax values at 30°C and pH 5.0 were calculated for the enzyme acting on glycogen, amylopectin, amylose, soluble starch, short chain amylose and maltose.
