Interaction of the synthetic ultimate carcinogens, N-sulfonoxy- and N-acetoxy-2-acetylaminofluorene, and of enzymatically activated N-hydroxy-2-acetylaminofluorene with nucleophiles

The interaction of four cellular nucleophiles with the putativeultimate carcinogens N-sulfonoxy-2-ring-³H]acetylamino-fluorene(N-sulfonoxy-2-AAF) and N-acetoxy-2-ring-³H] acetylaminofluorene(N-acetoxy-2-AAF), and with N-hydroxy-2-ring-³H]acetylaminofluorene(N-hydroxy-2-AAF) activated to the ultimate carcinogens by enzymaticsulfonation or trans-acetylation was determined. The adductswere isolated and adduct formation was quantified by isotopedilution. The order of nucleophilicity of the acceptors wasguanosine > tRNA polyguanylic acid (poly G) > N-acetyl-L-methioninewhen N-sulfonoxy-2-AAF, N-acetoxy-2-AAF or N-hydroxy-2- AAFactivated by transacetylation were the electrophiles. In thecase of N-hydroxy-2-AAF activated by enzymatic sulfonation,the order of nucleophilicity was N-acetyl-L-methionine >guanosine tRNA > poly G. The increase in the reactivityof N-acetyl-L-methionine is hypothesized to be due to cytosolicenzyme(s) which facilitate transfer of the methionine residuefrom the nitrogen to carbon atoms 3 and 1 of the fluorene moiety.Of the two synthetic esters, N-sulfonoxy-2- AAF exhibited greaterelectrophilicity than N-acetoxy-2-AAF. The rate of adduct formationof N-sulfonoxy-2-AAF and of N-acetoxy-2-AAF with each nucleophilewas a function of nucleophile concentration, indicative of abimolecular reaction mechanism. The interaction is thought toinvolve attack of the nucleophile on the uncharged ultimatecarcinogen, although interaction with an ion pair cannot beeliminated. The mutagenicity of N-sulfonoxy-2-AAF, N-acetoxy-2-AAFand of enzymatically activated N-hydroxy-2-AAF was evaluatedby the Ames test. N-Sulfonoxy-2-AAF was virtually inactive,while N-acetoxy-2-AAF exhibited weak mutagenicity. N-Hydroxy-2-AAFactivated by enzymatic sulfonation exhibited greater mutagenicitythan synthetic N-sulfonoxy-2-AAF. The mutagenicity and reactivityof ultimate carcinogens derived from N-hydroxy-2-AAF by enzymaticactivation do not necessarily coincide with the mutagenicityand reactivity of the synthetic ultimate carcinogens.