PHOSPHORYLATING GLYCOLYSIS IN THE EARLY CHICK EMBRYO

Abstract

From an ext,ensive series of experiments with whole embryos and with tissue mince, Needham and his coworkers (l-7) concluded that in the early chick embryo the phosphorylation route of glycolysis, the Meyerhof-Embden cycle, is imperfectly established. Because glycogen generally failed to be converted to lactic acid, they argued that the enzyme esterifying glycogen was absent or insufficient. Since they could demonstrate no breakdown of hexose diphosphate beyond triose phosphate, they maintained that the “dismutase” forming phosphoglycerate and lactate from triose phosphate and pyruvate was similarly lacking or insufficient. Though extracts of chick embryo were strongly positive with the glucose dehydrogenase and growth rate tests with Bacillus injluenzae, they gave negative results with the malic dehydrogenase system. The authors therefore concluded that coenzyme I, essential for the operation of the Meyerhof-Embden cycle, was absent from the chick embryo. Their study of the phosphorus compounds in trichloroacetic acid extracts of the embryo revealed between 5 and 7 mg. per cent of adenyl pyrophosphat,e phosphorus. This quantity the authors presumably considered insufficient for the phosphorylation pathway in glycolysis, since they listed as the fourth deficiency in this pathway the lack of adenyl pyrophosphate. In 1940, Meyerhof and Perdigon (8) succeeded in preparing extracts of early chick embryos which would readily glycolyze hexose diphosphate, in the presence of added coenzyme I. The ability of these extracts to form lactic acid from hexose diphosphate and pyruvate demonstrates the presence of the triose phosphate dehydrogenase which Needham considered lacking. In view of Needham’s emphasis on the importance of cell structure for the presumed non-phosphorylating glycolysis mechanism but not for the phosphorylating one, it is interesting to note how Meyerhof and Perdigon extracted the embryos. To obtain actively glycolyzing extracts, they had