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N-Hydroxyarylamine O-Acetyltransferase of Salmonella typhimurium: Proposal for a Common Catalytic Mechanism of Arylamine Acetyltransferase Enzymes

Masahiko Watanabe, Takako Igarashi, Tsuguchika Kaminuma, Toshio Sofuni and Takehiko Nohmi
Environmental Health Perspectives
Vol. 102, Supplement 6: Carcinogenic and Mutagenic N-Substituted Aryl Compounds (Oct., 1994), pp. 83-89
DOI: 10.2307/3432157
Stable URL: http://www.jstor.org/stable/3432157
Page Count: 7
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
N-Hydroxyarylamine O-Acetyltransferase of Salmonella typhimurium: Proposal for a Common Catalytic Mechanism of Arylamine Acetyltransferase Enzymes
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Abstract

Acetyl-CoA:N-hydroxyarylamine O-acetyltransferase is an enzyme involved in the metabolic activation of N-hydroxyarylamines derived from mutagenic and carcinogenic aromatic amines and nitroarenes. The O-acetyltransferase gene of Salmonella typhimurium has been cloned, and new Ames tester substrains highly sensitive to mutagenic aromatic amines and nitroarenes have been established in our laboratory. The nucleotide sequence of the O-acetyltransferase gene was determined. There was an open reading frame of 843 nucleotides coding for a protein with a calculated molecular weight of 37, 177, which was close to the molecular weight of the O-acetyltransferase protein determined by using the maxicell technique. Only the residue of Cys69 in O-acetyltransferase of S. typhimurium and its corresponding residue ( Cys68) in N-acetyltransferase of higher organisms were conserved in all acetyltransferase enzymes sequenced so far. The amino acid sequence Arg-Gly-Gly-X-Cys, including the Cys69, was highly conserved. A mutant O-acetyltransferase of S. typhimurium, which contained Ala69 instead of Cys69, no longer showed the activities of O- and N-acetyltransferase. These results suggest that the Cys69 of S. typhimurium and the corresponding cysteine residues of the higher organisms are essential for the enzyme activities as an acetyl-CoA binding site. We propose a new catalytic model of acetyltransferase for S. typhimurium and the higher organisms.

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