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Elaboration of Pyrimidine-specific Nucleosidases by Human Lymphoblastoid Cells of Established Cultures¹

Department of Medicine B, Roswell Park Memorial Institute, New York State Department of Health, Buffalo, New York 14263

Pyrimidine-specific nucleosidases were released rapidly by human lymphoblastoid cells of established cultures when incubated under certain culture conditions having no adverse affect on their viability or morphology. Nucleosidase production was not restricted to any particular type of lymphoblastoid line; enzymes with a high level of activity were elaborated by cells of cultures initiated from healthy subjects and patients with uncontrolled lymphocytic or myelocytic leukemia, as well as by cells of cultures exhibiting mostly B- or T-cell properties.

Tritiated thymine and uracil, which were not incorporated to any appreciable extent by DNA- and RNA-synthesizing cells, were identified by paper chromatography as the primary products arising from nucleosidase degradation of radiolabeled thymidine, uridine, and cytidine. Neither adenosine nor guanosine was catabolized.

These heat-labile and ultraviolet-sensitive enzymes with a molecular weight of 5 to 10 x 10⁴ did not affect the viability, morphology, or proliferation of lymphocytes in mitogenactivated cultures, lymphoblastoid cells in long-term cultures, or fibroblasts in monolayer cultures.

¹ This investigation was supported by USPHS Research Grant CA-17658 from the National Cancer Institute, Grant RR-05648 from the NIH, and Grant IN-54-N7 from the American Cancer Society.

Received 2/ 3/76. Accepted 4/23/76.