In vitro synthesis of particulate glycogen from uridine diphosphate glucose : II. Some studies on the growth process

Abstract

It was found that for the same extent of synthesis, the glycogen synthesized in vitro by liver glycogen synthetase (uridine diphosphate glucose: α-1,4-glucan α-4-glucosyltransferase, EC 2.4.1.11) from uridine diphosphate glucose is heavier than that synthesized from glucose 1-phosphate by muscle phosphorylase b (α-1,4 glucan:orthophosphate glucosyltransferase, EC 2.4.1.1). This result could be due to the different specificity of both transferring enzymes toward the molecular weight of the acceptor glycogen and to the incomplete use of the primer by glycogen synthetase. Glycogen synthesized from uridine diphosphate glucose showed a single light population in the first stages of synthesis. Later on, a clearly distinguishable heavier population appeared while the initial light peak was slightly shifted toward a higher molecular weight. The synthesis of glycogen from glucose 1-phosphate proceeded in a rather different way: only a single peak appeared during the synthesis. The molecular weight of this population increased as synthesis went on. An aggregation of the molecules of glycogen during synthesis from uridine diphosphate glucose could explain some of the results obtained.