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A New Deoxyuridine-5'-triphosphatase in Yoshida Sarcoma Cells Involved in Deoxyuridine 5'-Triphosphate Metabolism¹

Department of Enzyme Physiology, Institute for Enzyme Research, School of Medicine, Tokushima University, Kuramoto-Cho, Tokushima 770, Japan

A magnesium-independent deoxyuridine-5'-triphosphatase was found in Yoshida sarcoma cells but not in normal rat liver. The phosphatase is specific for deoxyuridine 5'-diphosphate and deoxyuridine triphosphate, and its K_m for deoxyuridine triphosphate is 2.7 x 10^-7 M. The enzyme was not inhibited by fluoride and required no divalent cations. Thus it differs from known nucleotide phosphatases.

Deoxyuridine monophosphokinase, which is detectable in a crude extract of normal rat liver, could not be detected in an extract of Yoshida sarcoma cells. However, with hydroxylapatite column chromatography of the extract, a deoxyuridine 5'-monophosphate kinase activity as high as that in normal rat liver was found in fractions separated from the phosphatase activity. Thus the absence of detectable deoxyuridine 5'-monophosphate kinase activity in the crude extract of Yoshida sarcoma cells is due to the presence of this nucleotide phosphatase.

¹ This work was supported in part by a grant-in-aid for cancer research from the Ministry of Health and Welfare, and by a grant-in-aid for scientific research from the Ministry of Education, Science, and Culture, Japan.

² Present address: Institute for Protein Research, Osaka University, Suita, Osaka 565, Japan.

Received 10/13/75. Accepted 1/18/77.