The glucoamylase of Coniophora cerebella

Abstract

The major amylolytic enzyme in culture filtrates of Coniophora cerebella grown in starch-containing media has been purified and characterized as a glucoamylase (EC 3.2.1.3). The activity/unit wt. of protein was increased 11-fold and the enzyme showed 1 major component on polyacrylamide-gel electrophoresis. The glucoamylase had optimum pH 4.0-4.5. Hg2+ completely inhibited the enzyme, but other ions tested had little effect on the activity at the concentration of ions used (5 mM). The action of the enzyme on amylopectin, amylose and maltose was studied. Hydrolysis proceeded by the stepwise removal of glucose units from the non-reducing ends of the polymer chains, and the enzyme was able to bypass or to hydrolyse the [alpha]-(1 [forward arrow] 6)-glucosidic linkages at branch points in the amylopectin molecule. Glucose was the only product found in digests of these substrates. At the same substrate concentration (0.1%, w/v) and enzyme concentration, the initial rates of glucose production from amylopectin, amylose and maltose were in the proportions 40:10:1. Km values at 40[degree] and pH 4.0 were calculated for the enzyme acting on amylopectin, amylose and maltose.