Some factors influencing the formation of Robison ester from glycogen and inorganic phosphate in muscle extract

Abstract

Parnas & Ostern [1936], have shown that inorganic phosphate can react with glycogen in presence of muscle extract to form Robison ester, i.e. a mixture of reducing hexosemonophosphates, discovered in yeast by Robison [1922] and first found in muscle, where the % of the individual components differs from that in yeast, by Embden & Zimmermann [1927]. The hexosemonophosphate formation from glycogen was claimed to be direct and not a secondary phosphorylation of glucose formed by hydrolysing enzymes. Balance experiments showed that the final glycogen plus hexosemonophosphate could account for all the initial carbohydrate. The authors called the formation of Robison ester a phosphorylysis of carbohydrate to distinguish it from the hydrolysis by amylase. Cori & Cori [1936; 1937], using washed muscle residue and welldialysed extract, detected the formation of a hexosemonophosphate other than Robison ester from glycogen and inorganic phosphate. The new ester was non-reducing yet Robison ester was readily formed from it after addition of Mg. It was identified as glucose-lphosphate [Cori et al. 1937]. The formation of the Cori ester is increased by adenylic acid; an action not yet quite explained, but apparently not due to phosphate transport by the adenylic acid. (The Coris call the enzyme producing the 1-ester phosphorylase; the one which produces the 6-ester from the Cori ester phosphoglucomutase.) To study the formation of Robison ester in muscle extracts is of interest as this step may be a key reaction of carbohydrate breakdown, both oxidative and anaerobic [Engelhardt & Barchash, 1938]. In the latter case Robison ester