Cloning and regulation of cholesterol 7α-hydroxylase, the rate-limiting enzyme in bile acid biosynthesis

Diane F. Jelinek, Stefan Andersson, Clive A. Slaughter, David W. Russell

Research output: Contribution to journalArticle

267 Citations (Scopus)

Abstract

The rate-limiting step in bile acid biosynthesis is catalyzed by the microsomal cytochrome P-450 cholesterol 7α-hydroxylase (7α-hydroxylase). The expression of this enzyme is subject to feedback regulation by sterols and is thought to be coordinately regulated with enzymes in the cholesterol supply pathways, including the low density lipoprotein receptor and 3-hydroxy-3-methylglutaryl-coenzyme A reductase and synthase. Here we report the purification of rat 7α-hydroxylase and the determination of a partial amino acid sequence. Oligonucleotides derived from peptide sequence were used to clone a full-length cDNA encoding 7α-hydroxylase. DNA sequence analysis of the cDNA revealed a 7α-hydroxylase protein of 503 amino acids with a predicted molecular weight of 56,890 which represents a novel family of cytochrome P-450 enzymes. Transfection of a 7α-hydroxylase cDNA into simian COS cells resulted in the synthesis of a functional enzyme whose activity was stimulated in vitro by the addition of rat microsomal cytochrome P-450 reductase protein. RNA blot hybridization experiments indicated that the mRNA for 7α-hydroxylase is found only in the liver. The levels of this mRNA increased when bile acids were depleted by dietary cholestyramine and decreased when bile acids were consumed. Dietary cholesterol led to an increase in 7α-hydroxylase mRNA levels. The enzymatic activity of 7α-hydroxylase paralleled the observed changes in mRNA levels. These results suggest that bile acids and sterols are able to alter the transcription of the 7α-hydroxylase gene and that this control explains the previously observed feedback regulation of bile acid synthesis.

Original languageEnglish (US)
Pages (from-to)8190-8197
Number of pages8
JournalJournal of Biological Chemistry
Volume265
Issue number14
StatePublished - May 15 1990

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Cholesterol 7-alpha-Hydroxylase
Cloning
Biosynthesis
Mixed Function Oxygenases
Bile Acids and Salts
Organism Cloning
Enzymes
Messenger RNA
Complementary DNA
Sterols
Cytochrome P-450 Enzyme System
Rats
Hydroxymethylglutaryl-CoA Synthase
Cholestyramine Resin
Feedback
Dietary Cholesterol
Amino Acids
NADPH-Ferrihemoprotein Reductase
LDL Receptors
COS Cells

ASJC Scopus subject areas

  • Biochemistry

Cite this

Cloning and regulation of cholesterol 7α-hydroxylase, the rate-limiting enzyme in bile acid biosynthesis. / Jelinek, Diane F.; Andersson, Stefan; Slaughter, Clive A.; Russell, David W.

In: Journal of Biological Chemistry, Vol. 265, No. 14, 15.05.1990, p. 8190-8197.

Research output: Contribution to journalArticle

Jelinek, Diane F. ; Andersson, Stefan ; Slaughter, Clive A. ; Russell, David W. / Cloning and regulation of cholesterol 7α-hydroxylase, the rate-limiting enzyme in bile acid biosynthesis. In: Journal of Biological Chemistry. 1990 ; Vol. 265, No. 14. pp. 8190-8197.
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