Regulation of Mytilus galloprovincialis glycogen phosphorylase by glucose and glucose-6-phosphate

A different glucose and glucose-6-phosphate inhibition of glycogen phosphorylase from Mytilus mantle relative to those of vertebrates has been demonstrated. Glucose and glucose-6-phosphate do not inhibit the a form (phosphorylated form), but they are competitive inhibitors for the substrate glucose-1-phosphate in the b form (unphosphorylated form), with Ki values of 190 and 0.2-0.3 mM, respectively. The results cast doubt on the role of glucose as a regulator and suggest that glucose-6-phosphate is a major regulator of glycogen phosphorylase activity in Mytilus mantle tissue because of its special relationship with gametogenesis.