The role of adenosine‐tri‐phosphate in phosphate transfer from yolk to other proteins in the developing frog egg. I. General properties of the transfer system as a whole

Abstract

Several proteins extractable from frog's eggs in early stages of development are able to split inorganic phosphate from adenosine-tri-phosphate (ATP) (Barth and Jaeger, '47). The egg also contains a phosphoproteiri phosphatase (PPPase) and an endogenous substrate for this enzyme, as demonstrated first by Harris ('46) and later by Peinsteiii arid Yolk ('49). Harris suggested that the PPPase liberates phosphate from the stored phosphoprotein of yolk to meet the metabolic needs of the developing embryo. Our interest in ATPases as based on the hypothesis that such enzymes might function in the transfer of energy to proteinr significant for differentiation.Extracts made in dilute KC1 o r 10% NaCl at plI 6.8 contain both the ATPase and the phosphoprotein phosphatase (PPPase). The pH at which these enzyme mixtures are incubated, however, has a profound effect on the aniourit of inorganic phosphate measurable at the end of a given interval. The PPPase has a pHactivity range of pH 3.0-6.8, with a iiiaximum at pH 5.0, whereas ATPase activity can be dernonstrntd in the alkaline range from pH 6.8-9.2 where the PPPase is inactive. That the ATPase may be active also in the acid range Aided by a grant froill The Committee on Growth acting for The Amerlcaii Cnriccr Society arid a grant from The Rockefeller Fomlclation. 413

Electron Microscopy of Growing Oocytes of Rana Pipiens

“…The necessary enzymes must persist in the cytoplasm immediately surrounding each growing platelet and may even be adsorbed on its surface. Two enzymes, phosphoprotein phosphatase and phosphotransferase, are known to be closely associated with yolk platelets (Harris, 1946;Barth and Jaeger, 1950). That the peripheral endoplasm remains a site of continued renewal of the yolk-synthesizing enzymes throughout the period of growth of the oocyte is evident from the cytological observation that small yolk platelets continue to form there.…”