Phosphorylase b Covalently Bound to Glycogen: Properties of the Complex

Publisher Website
Google Scholar
Abstract
Rabbit skeletal muscle glycogen phosphorylase b (EC 2.4.1.1) was covalently bound to oyster glycogen by means of cyanogen bromide. Removal of the unbound enzyme was achieved, using DEAE-Sephadex A-50 chromatography. Glycogen-bound phosphorylase b showed a higher affinity toward glucose 1-phosphate but a lower homotropic cooperativity, with respect to AMP activation, than the native enzyme. However, at low AMP concentrations conjugated phosphorylase b was efficient as the free enzyme. Glycogen-bound phosphorylase b exhibited catalytic activity upon its polysaccharide carrier. Kinetics of heat and cold inactivation indicated that the bound enzyme was considerably more resistant toward heat inactivation but less stable upon exposure to cold. Both conjugated and native enzymes had identical pH optima, similar activity/temperature dependencies and the same resistance against trypsin inactivation.