title: Spectral evidence for a liver mitochondrial cytochrome P450 involved in bile acid metabolism.
abstract: Optical difference spectroscopy of liver mitochondria has revealed the presence of a cytochrome P450 species by its ligand reactions with carbon monoxide, metyrapone and diethylphenylphosphine. Its concentration of 0.15 nmol/mg mitochondrial protein is high enough to be detectable by ESR also. A microsomal contamination of the mitochondria could be excluded. Mitochondrial cytochrome P450 forms an enzyme-substrate complex with 5beta-cholestane-3alpha, 7alpha, 12alpha-triol with Ks value very similar to the Km value of the 26-hydroxylation of this substrate. This supports the existence in liver mitochondria of a cytochrome P450-dependent 26-monooxygenase for bile acid precursors, as previously postulated by us on the basis of a photochemical action spectrum.
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D008797:Metyrapone / Q000494:pharmacology; D008862:Microsomes, Liver / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism*; D009943:Organophosphorus Compounds / Q000494:pharmacology; D010084:Oxidation-Reduction; D011485:Protein Binding; D051381:Rats; D013053:Spectrophotometry; D013261:Sterols / Q000378:metabolism*
chemical_list: D009943:Organophosphorus Compounds; D013261:Sterols; D002248:Carbon Monoxide; D003577:Cytochrome P-450 Enzyme System; D008797:Metyrapone