title: Heteroatom substitution shifts regioselectivity of lauric acid metabolism from omega-hydroxylation to (omega-1)-oxidation.
abstract: In contrast to several isoforms of cytochrome P450 (including 1A1, 1A2, 2B1, 2C2, 2C6 and 2E1), cytochrome P450 4A1 and a fusion protein derived from it, show a strong preference for hydroxylation of lauric acid (C12) at the less chemically reactive omega-CH3 group instead of the more reactive (omega-1)-CH2 group. We have explored the interplay of steric effects on substrate binding vs chemical reactivity at various substrate loci in determining the striking difference in regioselectivity of CYP2B1 and a 4A1-derived fusion protein, through studies with heteroatom substituted analogs of lauric acid, i.e., 10-methoxydecanoic acid and 10-methylthiodecanoic acid. With both enzymes the former undergoes simple omega-hydroxylation (giving 10-hydroxydecanoic acid and HCHO), but the latter undergoes facile S-oxidation at the omega-1 position instead of omega-hydroxylation. The dramatic shift in the regioselectivity of the fusion protein toward the thia analog is consistent with the greater length of C-S bonds and the greater atomic radius and polarizability of sulfur lone-pair electrons within an otherwise restrictive active site.
authors.affiliation: Department of Medicinal Chemistry, University of Kansas, Lawrence 66045-2506, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Alterman
authors.forename: C S
authors.initials: CS
authors.lastname: Chaurasia
authors.forename: P
authors.initials: P
authors.lastname: Lu
authors.forename: R P
authors.initials: RP
authors.lastname: Hanzlik
mesh_terms: D000818:Animals; D002994:Clofibrate / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000378:metabolism*; D004790:Enzyme Induction; D008401:Gas Chromatography-Mass Spectrometry; D006900:Hydroxylation; D007527:Isoenzymes / Q000096:biosynthesis / Q000378:metabolism*; D007850:Lauric Acids / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D010084:Oxidation-Reduction; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D007527:Isoenzymes; D007850:Lauric Acids; D011993:Recombinant Fusion Proteins; C030358:lauric acid; D003577:Cytochrome P-450 Enzyme System; D002994:Clofibrate; D010634:Phenobarbital