title: The effect of the nitrosourea analog of thymidine, 3'-[3-(2-chloroethyl)-3-nitrosoureido]-3'-deoxythymidine, on Escherichia coli thymidine kinase.
abstract: Escherichia coli thymidine kinase (ATP:thymidine 5'-phosphotransferase, EC 2.7.1.21) is irreversibly inactivated by incubation with 3'-[3-(2-chloroethyl)-3-nitrosoureido]-3'-deoxythymidine (3'-CTNU). The inactivation of the enzyme followed first-order kinetics even after loss of 96% of the original activity. This indicates that the inactivation process is a one-kill phenomenon and not a generation of less active enzyme. The addition of a preincubated aqueous solution of 3'-CTNU to the enzyme reaction mixture did not inactivate the enzyme. ATP . Mg2+ but not thymidine protects the enzyme from inactivation by 3'-CTNU. The allosteric regulators, dTTP, dCTP and dCDP also afforded complete protection of the enzyme from inactivation by 3'-CTNU. These data indicate that the dimer form of the enzyme is completely resistant to inactivation by 3'-CTNU, but the monomer form of the enzyme is sensitive. The specificity of the protection is supported by the finding that neither ATP . Mg2+ nor thymidine protect yeast alcohol dehydrogenase from inactivation by this nitrosourea analog of thymidine.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000494:Allosteric Regulation; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015224:Dideoxynucleosides; D004926:Escherichia coli / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D009607:Nitrosourea Compounds / Q000494:pharmacology*; D013936:Thymidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013937:Thymidine Kinase / Q000037:antagonists & inhibitors*
chemical_list: D000970:Antineoplastic Agents; D015224:Dideoxynucleosides; D009607:Nitrosourea Compounds; C027799:3'-(3-(2-chloroethyl)-3-nitrosourea)-3'-deoxythymidine; D000255:Adenosine Triphosphate; D013937:Thymidine Kinase; D008274:Magnesium; D013936:Thymidine