title: Inhibition of acetyl-coenzyme A dependent activation of N-hydroxyarylamines by phenolic compounds, pentachlorophenol and 1-nitro-2-naphthol.
abstract: Pentachlorophenol (PCP) and 1-nitro-2-naphthol were found to be potent inhibitors of enzymatic acetyl-CoA dependent activation, which is suggested as proceeding through direct O-acetylation, of N-hydroxyarylamines to tRNA binding by liver cytosolic enzymes from hamsters and rats. IC50 values of PCP for the activation of 2-hydroxyamino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (N-OH-Glu-P-1), 3-hydroxyamino-1-methyl-5H-pyrido[4,3-b]indole (N-OH-Trp-P-2) and N-hydroxy-2-aminofluorene (N-OH-AF) were 20, 25 and 17 microM, respectively, in hamster cytosol system. Similar inhibition was observed with rat liver cytosol (IC50 values of PCP and 1-nitro-2-naphthol were 13 and 12 microM, respectively, for the binding of N-OH-Glu-P-1). PCP is known as an inhibitor of sulfotransferase; however, another potent inhibitor of sulfotransferase, 2,6-dichloro-4-nitrophenol, did not inhibit the acetyl-CoA dependent binding. Antibiotic thiolactomycin, which inhibits bacterial O-acetyltransferase, did not affect the activation by hamster and rat cytosol, indicating the difference in property between bacterial and mammalian enzymes. The kinetic data obtained with hamster cytosol suggested the competitive inhibition of PCP with substrate, N-OH-Glu-P-1, and non-competitive inhibition with acetyl-CoA. In addition to the O-acetylation, PCP and 1-nitro-2-naphthol also inhibited N-acetylation of arylamines and N,O-acetyltransfer reaction of N-hydroxy-2-acetylaminofluorene (N-OH-AAF) by hamster cytosol. IC50 values for these two types of acetyltransfer reactions, however, were slightly higher than those observed for acetyl-CoA dependent activations of N-hydroxyarylamines.
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism*; D000818:Animals; D002243:Carbolines / Q000494:pharmacology*; D002733:Chlorophenols / Q000494:pharmacology*; D006224:Cricetinae; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D005449:Fluorenes / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008647:Mesocricetus; D009281:Naphthalenes / Q000494:pharmacology*; D010416:Pentachlorophenol / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D002243:Carbolines; D002733:Chlorophenols; D005449:Fluorenes; D007093:Imidazoles; D009281:Naphthalenes; C001368:N-hydroxy-2-aminofluorene; D000105:Acetyl Coenzyme A; C023786:2-hydroxyamino-6-methyldipyrido(1,2-a-3',2'-d)imidazole; C027210:3-hydroxyamino-1-methyl-5H-pyrido(4,3-b)indole; C016614:1-nitronaphthalene; D010416:Pentachlorophenol