PHOSPHOSERINE PHOSPHATASE DISTRIBUTION IN NORMAL AND NEOPLASTIC RAT TISSUES

Optimal conditions for assay of phosphoserine phosphatase by phosphate release were determined in dialyzed rat tissue extracts. Hydrolysis that was specifically inhibited by 10 mm l-serine was used to measure the enzyme activity. Nonspecific reactions were minimal. Phospho-d-serine was the preferred substrate since it avoided inhibition by the product of the reaction. Significant activities were present in normal adult kidney, liver, spleen, and brain, and extremely low activities in heart and breast. Relatively high activities in fetal liver, lactating mammary gland, and tumors suggested a parallel between enzyme level and tissue growth or protein synthesis. Marked activity changes occurred physiologically with development of liver and kidney. © 1969.