A Partial Purification and Characterization of a Phosphoanhydride Hydrolase (Phosphoprotein Phosphatase) from the Frog Egg
Daniel L. Harris 1, Bernard J. Mizock 1, and Simon J. Pilkis 1
From the
1 From the Department of Physiology, University of Chicago, Chicago, Illinois
Methods for the partial purification of the phosphoprotein phosphatase of the frog egg are described. The enzyme is soluble in distilled water, is heat stable, and is not inactivated by 1 m acetic acid or 0.1 n Na2CO3. The pH optimum (3.0) is unusually low. The enzyme is inhibited competitively by phosphate and molybdate. The enzyme has no activity on the internal pyrophosphates of dinucleotides and similar compounds, on phosphoramidates, or on aliphatic phosphate esters. The enzyme is active on a long series of acyl phosphates: organic and inorganic polyphosphates, both long and short chains and small rings; aromatic phosphates; phosphoenolpyruvate; acetyl phosphate; and carbamyl phosphate. It is less active on phosphoproteins.
Evidence is presented which suggests that these activities are all due to one enzyme. The enzyme most closely resembles the phosphoprotein phosphatase of spleen but differs from the latter in several critical respects. The implications of these findings are examined. It is suggested that the enzyme is better classified as a nonspecific phosphoanhydride hydrolase than as a phosphoprotein phosphatase.
Submitted on September 13, 1965
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