title: Covalent binding of 4-carbamoylbenzenediazonium chloride to deoxyguanine bases of DNA resulting in apparent irreversible inhibition of poly(adenosine diphosphoribose) polymerase at the nicotinamide binding site.
abstract: The poly(adenosine diphosphoribose) polymerase activity of isolated liver nuclei was inhibited by 4-carbamoylbenzenediazonium chloride, referred to as 4-diazoniobenzamide, an effect that was dependent on the time of incubation and the concentration of the diazonium compound, with inhibition following first-order kinetics. The inhibition was not reversed by reisolation of nuclei and centrifugal washing, whereas the inhibition by benzamide or 4-aminobenzamide was completely reversible under these conditions. Simultaneous incubation of 4-diazoniobenzamide with benzamide prevented enzyme inhibition. The 4-diazoniobenzoic acid analogue was not inhibitory. The mechanism of action of 4-diazoniobenzamide was traced to a specific covalent binding to dGMP of DNA to form N2-[(4-carbamoylphenyl)azo]-2'-deoxyguanosine 5'-monophosphate. Coenzymic DNA, by tight association with the polymerase protein, fixes the -C(O)NH2 moiety of the adduct at the nicotinamide-binding site of the enzyme.
mesh_terms: D000818:Animals; D002417:Cattle; D002467:Cell Nucleus / Q000201:enzymology; D004247:DNA / Q000378:metabolism*; D003849:Deoxyguanosine; D003979:Diazonium Compounds / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology; D007202:Indicators and Reagents; D008099:Liver / Q000201:enzymology; D009536:Niacinamide / Q000378:metabolism*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D013950:Thymus Gland / Q000201:enzymology; D014316:Tritium
chemical_list: D003979:Diazonium Compounds; D007202:Indicators and Reagents; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D014316:Tritium; D009536:Niacinamide; C053221:4-carbamoylbenzenediazonium; D004247:DNA; D003849:Deoxyguanosine