Presence of D and I forms of glycogen synthase in adult frog liver.

Liver glycogen synthase from adult non-treated frogs is essentially completely dependent on glucose-6-P. Administration of glucose to the animals promotes the appearance of a form of glycogen synthase in absence of glucose-6-P. These two forms show different kinetic characteristics. The enzyme from glucose injected animals corresponds to an I form whereas the enzyme from non-treated animals appears to be a D form.