Acid α-D-Glucosidase Glucohydrolase from Cattle Liver

Abstract

Abstract Acid α-glucosidase has been isolated from cattle liver in ultracentrifugally and electrophoretically homogeneous form and partially characterized. The enzyme has a sedimentation constant of 5.7 S, a diffusion constant of 4.7 x 10-7 cm2. sec-1, and an average molecular weight, as determined by three different methods, of 107,000. The enzyme contains four —SH groups per molecule, and it is progressively inactivated by incubation at pH above 7, the inactivation being prevented by sulfhydryl group reagents. The highly purified enzyme catalyzes the hydrolysis of the α-(1→4) linkages of glycogen, maltose, and a synthetic glycoside (6-bromo-2-naphthyl-α-d-glucopyranoside) with a Km of 28 mg per ml, 1 x 10-2 m, and 4 x 10-3 m, respectively. Moreover, the enzyme hydrolyzes also the α-(1→6)-glucan linkages of dextran and isomaltose. The pH optimum is the same (4.5) for all these activities. Erythritol, Tris, and turanose inhibit the enzyme competitively, the inhibition constants being 2.7 x 10-2 m, 5.0 x 10-3 m, and 1.4 x 10-3 m, respectively.