Deoxyribonucleotide Phosphatase from Rat Liver and Cultured Mouse Fibroblasts

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Abstract
An enzyme which catalyzes the preferential dephosphorylation of the 5′‐phosphates of deoxythymidine, deoxyuridine and deoxyguanosine was purified 100‐fold from rat liver. The preparation appeared to be free from contaminating phosphatase activities. The dephosphorylation of deoxyribonucleotides was dependent on the presence of Mg2+ ions and had a pH optimum around 6.0. The Km value for the dephosphorylation of deoxythymidine 5′‐phosphate was 5.7 mM.High activities of the enzyme were found in cultured mouse fibroblasts. In parasynchronously growing cells no changes of enzyme activity were found during the cell cycle.