Clii. Factors Influencing the Formation of Robison

COMPOUNDS which influence Robison ester formation from glycogen and inorganic phosphate in muscle extract may act either on the first step: glycogen + inorganic phosphate='glucose-l-phosphate (Cori ester)-or on the second step: Cori ester-+hexose-6-phosphate (Robison ester), or on both these steps. Several factors which increase or inhibit Robison ester formation could be shown to act on one or the other of the two processes. Glucose inhibits the initial phosphorylation [Lehmann, 1938, 1; Cori et al. 1939]. Insulin influences the second step [Lehmann, 1938, 2, 3]. Hexosediphosphate activates the formation of Cori ester [Gill & Lehmann, 1939]. KCN and reduced glutathione increase Robison ester formation [Gill & Lehmann, 1939]. Cori et al. [1939] report that they could find no influence of KCN and reduced glutathione on Cori ester formation, which indicates that these factors act upon the second step, the conversion of Cori ester into Robison ester. In this paper experiments are reported which were performed to elucidate the exact point of attack of various factors. The methods used are identical with those given in a previous communication in greater detail [Gill & Lehmann, 1939]. The experiments were performed at 37°. When adenylic acid and Mg were added this is specially mentioned. The first was used as the Na salt and the second as the chloride. Old extracts were used and usually no coenzyme was added. It was found that under these conditions an appreciable amount of Cori ester was formed, the accumulation or disappearance of which it was possible to study. All values are expressed as mg. per ml. reaction mixture.