Doxynucleotide-polymerizing enzymes of calf thymus gland. IV. Inhibition of terminal deoxynucleotidyl transferase by metal ligands.
نویسندگان
چکیده
The polymerization of deoxynucleoside triphosphates, catalyzed by terminal deoxynucleotidyl transferase from calf thymus gland, is strongly inhibited by various metal chelators. The reaction appears to be first order with respect to enzyme, deoxynucleoside triphosphate, and initiator, indicating that there is only one catalytic center for each enzyme molecule. The presence of metal chelator does not affect the molecular state of the enzyme or the order of reaction. An analysis of the kinetics of o-phenanthroline inhibition demonstrates that the ligand is noncompetitive with nucleoside triphosphate substrate and strictly competitive with oligodeoxynucleotide initiator. These results, obtained in the presence of millimolar Mg(++), suggest that the initiator binds to the enzyme through a transition metal atom and ligand inhibition occurs at that site. The precise spatial arrangement of the coordination orbitals around a metal atom provides a model to visualize the specificity of the enzyme for the 3'-OH end of the growing polynucleotide chain.
منابع مشابه
Proteolytic degradation of calf thymus terminal deoxynucleotidyl transferase.
A high molecular weight preparation of terminal transferase containing 58,000- and 44,000-dalton peptides has been purified from calf thymus glands. The relationship of these terminal transferase peptides to the low molecular weight form was established with an immunoblot procedure using rabbit antibody directed against the homogeneous calf thymus low molecular weight terminal transferase (32,0...
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Terminal deoxynucleotidyl transferase was purified to homogeneity from the blasts of eight patients with leukemia and compared with purified transferase from normal human and calf thymus. In two cases phenylmethanesulfonylfluoride was added during purification to reduce proteolysis. Comparative kinetic analyses of the purified enzymes indicated no differences in catalytic properties. There was ...
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Terminal deoxynucleotidyl transferase, an enzyme which catalyzes the polymerization of deoxyribonucleoside triphosphates, elongating oligoor polydeoxynucleotide chains, but without direction from a nucleic acid template, is thought to be specific for thymus gland and thymusderived cells. We have confirmed the observations that high levels are characteristic of thymus gland with both human and c...
متن کاملTerminal deoxynucleotidyl transferase activities in human blood leukocytes and lymphoblast cell lines: high levels in lymphoblast cell lines and in blast cells of some patients with chronic myelogenous leukemia in acute phase.
Terminal deoxynucleotidyl transferase, an enzyme which catalyzes the polymerization of deoxyribonucleoside triphosphates, elongating oligo- or polydeoxynucleotide chains, but without direction from a nucleic acid template, is thought to be specific for thymus gland and thymus-derived cells. We have confirmed the observations that high levels are characteristic of thymus gland with both human an...
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ورودعنوان ژورنال:
- Proceedings of the National Academy of Sciences of the United States of America
دوره 65 4 شماره
صفحات -
تاریخ انتشار 1970