A primer independent activity of rabbit muscle phosphorylase b.

Rabbit muscle phosphorylase b was found to be capable of forming protein bound alpha-1,4 glucosyl chains upon incubation of the enzyme with appropriate concentrations of glucose-1-phosphate with no primer addition (unprimed synthesis). This activity would only be present in a small fraction of the total muscle phosphorylase b activity, as judged from the high concentrations of enzyme which are required to demonstrate the occurrence of unprimed synthesis. Polyacrylamide gel electrophoresis shows the presence of a phosphorylase isoenzyme capable of accepting glucosyl moieties, giving rise to a glucosylated protein enzymatically active in the chain lengthening of its own glucan.