Journal
BIOCHEMICAL PHARMACOLOGY
Volume 67, Issue 8, Pages 1445-1457Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.bcp.2003.12.023
Keywords
human cytochrome p450 1A1; CYP1A1; polyunsaturated fatty acid; arachidonic acid; eicosapentaenoic acid; vasoactive metabolite
Categories
Funding
- NCI NIH HHS [CA85542] Funding Source: Medline
- NCRR NIH HHS [RR16440] Funding Source: Medline
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Human cytochrome P450 1A1 (CYP1A1) and human NADPH-cytochrome P450 reductase were expressed and purified from Spodoptera frugiperda insect cells. A reconstituted enzymatically active system metabolized polyunsaturated fatty acids such as arachidonic (AA) and eicosapentaenoic acid (EPA). CYP1A1 was an AA hydroxylase which oxidizes this substrate at a rate of 650 +/- 10 pmol/min/nmol CYP1A1, with over 90% of metabolites accounted for by hydroxylation products and with 19-OH-AA as major product. Epoxyeicosatrienoic acid (EET), mainly 14,15-EET, accounted for about 7% of total metabolites. Unlike rat CYP1A1, the human enzyme exhibited no 20-OH-AA as product. In contrast, with EPA as substrate CYP1A1 was mainly an epoxygenase, oxidizing with over 68% of total metabolites EPA to 17(R), 18(S)-epoxyeicosatetraenoic acid (17(R), 18(S)-EETeTr). 19-OH-EPA accounted for about 31% of total metabolites. Significantly, the 17,18-olefinic bond of EPA was epoxidized to 17(R), 18(S)-EETeTr with nearly absolute regio- and stereoselectivity. Molecular modeling analyses provided rationale for high efficiency of AA hydroxylation at C 19 and its gradual decrease down to C-14, as well as for the limited EPA 17(S), 18(R) epoxidation due to unfavorable enzyme-substrate interactions. The absence of omega-hydroxylation for both substrates is not due to steric factors, but probably a consequence of different reactivities of omega and (omega - 1) carbons for hydrogen abstraction. It is suggested that the capacity of human CYP1A1 to metabolize AA and EPA and its inducibility by polycyclic aromatic hydrocarbons may affect the production of physiologically active metabolites, in particular, in the cardiovascular system and other extrahepatic tissues including lung. (C) 2004 Elsevier Inc. All rights reserved.
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