Phosphorylation reactions in islets of Langerhans

The possible significance of phosphorylation reaction in islets of Langerhans in relation to the secretion of insulin is discussed. The secretagogues, glucose and its metabolites, cAMP and Ca++ and their influences on protein-kinase activity are given particular attention. The data obtained by the authors, as well as by other groups, are in agreement that cAMP is a potent stimulator of protein kinase activity. Glucose and its metabolites influenced protein kinase activity in one instance. Ca++ in supraphysiological amounts inhibited protein phosphorylation. The links between phosphorylation reactions and insulin secretion are, at the present time, conjectural.