Molecular Pharmacology, Vol 7, 381-388, Copyright © 1971 by the American Society for Pharmacology and Experimental Therapeutics

Acetylation of the Carcinogen N-Hydroxy-2-acetylaminofluorene by Acetyl Coenzyme A to Form a Reactive Ester

¹ Fels Research Institute and Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140

Nonenzymatic acetylation of various carcinogenic hydroxamic acids was studied with acetyl-1-¹⁴C-CoA as the acetyl donor. Formation of acetate esters was studied by determination of the benzene-extractable radioactivity. Interaction of these esters in vitro at pH 7.5 with methionine and guanosine was used as a measure of their reactivity.

N-Hydroxy-2-acetylaminofluorene was acetylated to a much greater extent than 2-aminofluorene, 2-acetylaminofluorene, or its ring-hydroxylated derivatives. The reaction was dependent on pH and the type of buffer, period of incubation, and the concentrations of acetyl-CoA and N-hydroxy-2-acetylaminofluorene. With 5 min of incubation and KHCO₃-KOH buffer, the pH optimum was found to be 10. On the basis of its ultraviolet absorption spectrum, R_F value after paper chromatography, lability to alkali, and characteristic reaction products with methionine and guanosine, the acetylated reaction product of N-hydroxy-2-acetylaminofluorene has been characterized as N-acetoxy-2-acetylaminofluorene. Among various N-hydroxy derivatives tested, N-hydroxyurethane and its N-methyl derivatives were acetylated most rapidly.

It is suggested that acetate esters of hydroxamic acids may also be some of the ultimate carcinogenic metabolites of carcinogenic hydroxamic acids.