Slow step in activation of muscle glycogen phosphorylase b by adenosine 5'-monophosphate.

The incubation of glycogen phosphorylase b from rabbit skeletal muscles with the allosteric activator (AMP) for 10-15 min has been found to result in an additional increase in the initial rate of the enzymatic reaction (v) as compared with the corresponding value of v measured by the initiation of the enzymatic reaction by the addition of a mixture of glucose 1-phosphate and AMP (0.02 M HEPES, pH 6.8; 37 degrees C). Glycogen with molecular mass of 270.10(6) daltons was used in the kinetic experiments. It is assumed that the enhancement of the rate of the phosphorylase b reaction is due to association of the enzyme molecules adsorbed to a glycogen particle resulting in an increase in the affinity of the enzyme for glycogen.