CHARACTERIZATION OF VARIOUS CLASSES OF PROTEIN ADDUCTS

Analysis of the types of protein adducts formed by chemical carcinogens indicate that adducts may be categorized into various classes according to the nature of the carcinogen as well as the amino acid with which they react. Tryptophan(214) of serum albumin was previously shown to react specifically with N-sulfonyloxy-N-acetyl-4-aminobiphenyl. The same residue is now shown to also react with the sulfate esters of N-hydroxy-N-acetyl-2-aminofluorene and N-hydroxy-N, N'-diacetylbenzidine. Thus, Trp-214 appears to be a binding site for a variety of activated N-aryl hydroxamic acids. Epoxides and diol epoxides derived from polynuclear aromatic hydrocarbons alkylate carboxylic groups in hemoglobin and serum albumin. Because the esters formed are readily hydrolyzed to dihydrodiols and tetrahydrotetrols which can be determined by GC-MS, it is possible to analyze for a wide range of polyaromatic hydrocarbon (PAH) epoxide adducts. With this approach it was shown that human subjects experiencing exposure to ambient levels of environmental PAH do take up and metabolize chrysene and benzo[a]pyrene. Feral, bottom-dwelling fish inhabiting contaminated waters were also examined. Globin adducts containing certain dihydroxy groups such as those arising in anti-diol epoxide adducts were concentrated by boronate affinity chromatography and further analyzed by HPLC with diode-array UV/visible detection. Four compounds were detected that exhibited spectra characteristic of a polynuclear chromophore. Two of these appeared to be isomers. Further instrumental analysis is needed to elucidate the structure of these unknown putative adducts. A discussion of how these analyses might be conducted as well as their extension to less heavily adducted human globin samples is presented.