title: Farnesol as an inhibitor and substrate for rabbit liver microsomal P450 enzymes.
abstract: Farnesol and the related isoprenoids, geranylgeraniol, geranylgeranyl pyrophosphate, and farnesyl pyrophosphate, are produced in the endoplasmic reticulum of hepatocytes in mammals, and each serve important biological functions. Of these compounds, only farnesol was shown to significantly inhibit rabbit liver microsomal cytochrome P450 enzymes. The observed inhibition appeared to be reversible, and was not strictly competitive, but rather mixed in nature. Of the activities examined, ethoxycoumarin de-ethylase and diclofenac-4-hydroxylase activities were most sensitive to farnesol, with K(I) and K(I)' values between 11 and 40 microM. Caffeine-8-hydroxylation and taxol-6-hydroxylation were not inhibited at all by farnesol. Farnesol appeared to be a P450 substrate, as well as an inhibitor, as indicated by the NADPH-dependent decrease in farnesol concentration in microsomal incubations, and the metabolism was inhibited by CO, which pointed to the involvement of P450 isozymes.
authors.affiliation: Department of Chemistry and Biochemistry, 405A Petty Science Building, The University of North Carolina at Greensboro, Greensboro, NC 27402-6170, USA. gmraner@uncg.edu
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Raner
authors.forename: April Q
authors.initials: AQ
authors.lastname: Muir
authors.forename: Clarice W
authors.initials: CW
authors.lastname: Lowry
authors.forename: Brian A
authors.initials: BA
authors.lastname: Davis
mesh_terms: D000818:Animals; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004224:Diterpenes / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005204:Farnesol / Q000493:pharmacokinetics / Q000494:pharmacology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D007700:Kinetics; D008862:Microsomes, Liver / Q000201:enzymology*; D011817:Rabbits; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D004224:Diterpenes; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D011994:Recombinant Proteins; D005204:Farnesol; D003577:Cytochrome P-450 Enzyme System; C017338:geranylgeraniol