Enzymatic Properties and Action Patterns ofThermoactinomyces vulgarisα-Amylase

Abstract

Thermoactinomyces vulgaris α-amylase was purified to an electrophoretically homogeneous state, and its properties and action on starch, pullulan, maltooligosaccharides and partial hydrolyzates of pullulan were studied. Both starch-hydrolyzing and pullulan-hydrolyzing activities of the enzyme were inhibited by Al³⁺, Cu²⁺, Hg²⁺, p-chloromercuribenzoate, maltotriitol, panitol, isopanitol and some microbial α-amylase inhibitors to nearly the same extent. Km and V_max values of the enzyme for short chain amylose (DP = 17) and pullulan, Ki values for sugar alcohols and α-amylase inhibitors, and the kinetics of the simultaneous presence of short chain amylose and pullulan supported the view that the hydrolytic action of the enzyme on starch and pullulan is due to a single catalytic site. Action patterns of the enzyme on maltooligosaccharides and partially hydrolyzed pullulan were examined, and it was suggested that this α-amylase can attack some of the (1 → 6)-α-d-glucosidic linkages in partial hydrolyzates of pullulan as well as (l → 4)-α-d-glucosidic linkages in starch and pullulan.