THE FORMATION OF GLUCOSE-l-PHOSPHORIC ACID IN EXTRACTS OF MAMMALIAN TISSUES AND OF YEAST

The initial stages of fermentation of glycogen to lactic acid in muscle have been investigated only recently. It was shown (1, 2) that the glycolytic reactions are initiated by the formation of glucose-l-phosphoric acid from glycogen and inorganic phosphate, an enzymatic process in which adenylic acid acts as coenzyme. The glucose-l-phosphoric acid (l-ester) is converted to glucose-6phosphoric acid by another muscle enzyme the activity of which is greatly enhanced by magnesium ions. Because of the presence of this enzyme and of magnesium the l-ester does not accumulate in intact muscle, but it can be made to accumulate in muscle extracts from which magnesium ions have been removed by long dialysis. The isolation of the l-ester from such extracts and its synthesis have been described (3). Embden ester (an equilibrium mixture of glucose-, fructose-, and probably also mannosed-phosphate (4)), here referred to as 6-ester, is always present in intact muscle; it is formed from glucose-6-phosphate by an enzyme which Lohmann (5) found in extracts of muscle, brain, liver, kidney, and yeast. With these three reactions the first stages of glycogen fermentation have been completed; then follow the phosphorylation of g-ester to fructosediphosphate and the reactions described in the Embden-Meyerhof scheme. It is shown in this paper that the formation of l-ester from glycogen and inorganic phosphate occurs in extracts of a variety of mammalian tissues and of yeast. The disruptive phosphorylation of glycogen, for which a scheme is presented, may therefore be regarded as a generally occurring process.