MOLECULAR MECHANISM OF THE CONTROL OF GLYCOGENOLYSIS BY CALCIUM-IONS AND CYCLIC-AMP IN THE MANTLE OF MYTILUS-GALLOPROVINCIALIS LMK

Glycogen phosphorylase b from the mantle of Mytilus galloprovincialis was incubated with phosphorylase kinase and ATP. The conversion of phosphorylase b (absolutely dependent on AMP for activity) to an equal amount of phosphorylase a (AMP-independent) was observed in response to the addition of calcium ions or cAMP. The two enzymatic forms have different responses to temperature and pH. PHosphorylase a can catalyze the degradation of tissue glycogen two to three times more efficiently than phosphorylase b. This result suggests that phosphorylation of this enzyme makes an important contribution to regulation of the degradation of glycogen during periods of high energy demand, for example, during anoxia.