Specific positions involved in enzyme catalyzed covalent binding of benzo[a]pyrene to poly(G).

Publisher Website
Google Scholar
Abstract
Covalent binding of the carcinogen benzo[a]pyrene [BaP] to poly(G) was studied with the use of a radioactive assay and specifically labeled substrates to define the role of the 1,3- and 6-positions of the hydrocarbon during this process. Binding was dependent on [rat liver] microsomes, NADPH, O2 and poly(G). 7,8-Benzoflavone and 2'',2''-diethylaminoethyl-2,2-diphenyl valerate were inhibitory whereas modulators of epoxide hydrase activity had little effect. 3H and14C studies suggested a possible loss of 1-2 protons. Incorporation of [6-3H1]BaP provided evidence that the 6-position of the hydrocarbon was not metabolized during covalent attachment to poly(G) and, results with [1,3,6-3H]BaP suggest that the 1- and 3-positions may not be involved either. After scaling up of the standard assay 20-fold, characterization of the BaP-poly(G) complex was done by hydrolysis and subsequent chromatography. TLC of the isolated hydrolysis products treated with HCl or alkaline phosphatase indicated that the complex formed between BaP and poly(G) was covalently linked and composed of hydrocarbon-nucleotide(s).