Formation of Glucose-1-Phosphoric Acid in Muscle Extract

Abstract

In recent experiments 1 on minced and washed frog muscle, adenylic acid, in amounts corresponding to 4 mg. P per 100 gm. muscle, increased very markedly the formation of hexosemono-phosphate. The small amount of phosphorylation which occurred without addition of adenylic acid was attributed to the presence of nucleotides which had not been removed by washing, since the washed muscle contained 2 to 4 mg. % of organic P.

The first phosphorylation product was found to be glucose-1-phosphoric acid which was isolated as the crystalline brucine salt and which has since been synthesized and identified as an α-compound. This is of significance in view of the fact that glycogen, the carbohydrate from which this ester is formed, consists of α-glucosidic linkages.

Glucose-1-phosphoric acid, when added to fresh muscle extract, is converted in a few minutes to hexose-6-phosphoric acid by a wandering of the phosphate group. The same change occurs in minced and washed muscle but at a slower rate, so that after short periods of incubation and with phosphorylation accelerated by the addition of adenylic acid, the rate of formation of the 1-ester exceeds its rate of conversion to the 6-ester, these being the conditions which made possible the isolation of the new ester.

The experiments in Table I show that a dialyzed rabbit muscle extract behaves in the same way as minced and washed frog muscle. Without addition of adenylic acid phosphorylation was slow and glucose-1-phosphoric acid did not accumulate in significant amounts. With adenylic acid added phosphorylation was increased about 4 times, resulting in an accumulation of glucose-1-phosphoric acid. Between 60 and 90 minutes phosphorylation no longer occurred and the gain in 6-ester (+3.5 mg.) was balanced by the decrease in 1-ester (—3.4 mg.).