A Phosphorylase in Calcifying Cartilage.

Abstract

It has been shown by histochemical1, 2, 3 and chemical3, 4 methods that cartilage cells preparatory to calcification accumulate large stores of glycogen, which disappear abruptly just prior to or during the early course of calcium deposition. The processes of glycogen depletion and of calcification appear to be closely courdinated, suggesting some inter-relation;1, 2 for example, phosphoric esters formed during glycogen breakdown might serve as substrates for bone phosphatase.2, 3, 4, 5 This inherently plausible hypothesis, as yet unsupported by direct evidence, has been largely ignored in current speculation concerning the mechanisms of calcification.In liver and muscle, according to recent studies by Cori,6 Parnas7 and others, the major pathway of glycogen degradation involves phosphorolysis and the formation of intermediate phosphoric esters. The glycogenolytic cycle is initiated by the reactionGlycogen + inorganic phosphate glucose-1-phosphatewhich is catalyzed by an enzyme, phosphorylase, shown to be...