title: Regio- and stereoselectivity of hepatic cytochrome P-450 toward polycyclic aromatic hydrocarbon substrates.
abstract: Although the cytochrome P-450 system shows broad substrate specificity toward the PAH, it also has regio- and stereoselectivity. Of the PAH substrates yet studied, phenanthrene is metabolized most efficiently, whereas chrysene and DBA are much more slowly turned over. Interestingly, the cytochrome P-450 system and epoxide hydrolase favor the formation of dihydrodiols with R,R configuration. The predominant enantiomers of the dihydrodiols with the bay-region double bond, as well as bay-region diol epoxides derived from phenanthrene, chrysene, BA and B[a]P, are superimposable when their bay-regions are aligned (Fig. 3). These metabolically favored isomers of the dihydrodiols and bay-region diol epoxides are also the more carcinogenic isomers when derived from carcinogenic polycyclic hydrocarbons.
mesh_terms: D000818:Animals; D001711:Biotransformation; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004851:Epoxide Hydrolases / Q000378:metabolism; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D010634:Phenobarbital / Q000494:pharmacology; D011083:Polycyclic Compounds / Q000378:metabolism*; D051381:Rats; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D011083:Polycyclic Compounds; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D004851:Epoxide Hydrolases; D010634:Phenobarbital