Cytochrome P450-dependent desaturation of lauric acid: Isoform selectivity and mechanism of formation of 11-dodecenoic acid

Xiangming Guan, Michael B. Fisher, Dieter H. Lang, Yi Min Zheng, Dennis R. Koop, Allan E. Rettie

Research output: Contribution to journalArticle

48 Scopus citations

Abstract

Cytochrome P450-catalyzed desaturation reactions have been reported infrequently in the literature. Previously, we documented the formation of the terminal olefinic metabolite of valproic acid by various members of the CYP2B and CYP4B sub-families. However, despite the extensive use of fatty acid substrates in drug metabolism studies, other examples of terminal desaturation at non- activated carbon centers are lacking. The goals of the present studies were to determine whether the archetypal P450 substrate, lauric acid (dodecanoic acid; DDA), also undergoes desaturation reactions, identify specific rabbit P450 isoforms which catalyze this reaction and examine its mechanism. A highly sensitive, capillary GC/MS assay was developed to separate and quantitate the trimethylsilyl derivatives of 1 l-ene-DDA, cis- and trans-10-ene- DDA and cis- and trans-9-ene-DDA. Among all of these potential olefinic metabolites, only 11-ene-DDA was formed at a significant rate by rabbit liver microsomes. The formation of 11-ene-DDA was NADPH-dependent, and was induced markedly by acetone pre-treatment but not by phenobarbital, rifampin or Arochlor 1254. Studies with seven purified, reconstituted rabbit P450 isoforms showed that the most rapid rates of desaturation were obtained with CYP2EI, CYP4A5/7 and CYP4BI. Non-competitive, intermolecular isotope effect experiments, conducted with [12,12,12-2H3]DDA and [11,112H]DDA, demonstrated further that CYP4Bl-mediated terminal desaturation of DDA is initiated by removal of a hydrogen atom from the w-1 rather than the ω position.

Original languageEnglish (US)
Pages (from-to)103-121
Number of pages19
JournalChemico-Biological Interactions
Volume110
Issue number1-2
DOIs
StatePublished - Mar 12 1998

Keywords

  • Cytochrome P450
  • Dehydrogenation
  • Isotope effect
  • Lauric acid
  • Mechanism
  • Rabbit liver

ASJC Scopus subject areas

  • Toxicology

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