Terminal Deoxyribonucleotidyl Transferase in Human Leukemia
Abstract
Terminal deoxyribonucleotidyl transferase (EC 2.7.7.31; nucleoside triphosphate:DNA nucleotidylexotransferase) is usually found only in thymus, but has been reported in leukemic cells from children with acute lymphoblastic leukemia. In an unusual adult patient with acute myelomonocytic leukemia, terminal transferase was found at a level of 16 units per 108 bone marrow cells and 14 units per 108 circulating leukocytes (1 unit = 1 nmol of nucleotide per hr). This activity is comparable to that found in normal thymus. Assays of transferase in marrow and peripheral leukocytes from patients with typical acute and chronic myelogenous leukemias gave average values of 0.5 and 0.3 unit per 108 cells, respectively. Transferase activity is also found in normal bone marrow at about 0.07 unit per 108 cells. Terminal deoxyribonucleotidyl transferase in all samples of human marrow and peripheral blood had reaction characteristics, sedimentation, and chromatographic properties similar to the homogeneous enzyme from calf thymus.
