Characterization of human sterol 27-hydroxylase: A mitochondrial cytochrome P-450 that catalyzes multiple oxidation reactions in bile acid biosynthesis

James J. Cali, David W. Russell

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283 Scopus citations


The enzyme sterol 27-hydroxylase catalyzes the first step in the oxidation of the side chain of sterol intermediates in the bile acid synthesis pathway. Human sterol 27-hydroxylase cDNAs were isolated from a liver cDNA library by cross-hybridization with a previously cloned rabbit cDNA probe. DNA sequence analysis of hybridization-positive clones predicted a human sterol 27-hydroxylase consisting of a 33-amino-acid mitochondrial signal sequence followed by a mature protein of 498 amino acids. RNA blotting experiments demonstrated sterol 27-hydroxylase mRNAs of approximately 1.8 to 2.2 kilobases in liver and fibroblast cells. The steady state levels of the mRNA did not change when cultured cells were grown in the presence or absence of sterols. Introduction of the sterol 27-hydroxylase cDNA into Simian COS cells resulted in the expression of active enzyme capable of catalyzing multiple oxidation reactions (R-CH3 → R-CH2OH → R-COOH) at carbon 27 of sterol intermediates of the bile acid synthesis pathway.

Original languageEnglish (US)
Pages (from-to)7774-7778
Number of pages5
JournalJournal of Biological Chemistry
Issue number12
StatePublished - Jul 22 1991


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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