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Cytochrome P450, family 8, subfamily B, polypeptide 1
Symbols CYP8B1 ; CP8B; CYP12
External IDs OMIM602172 MGI1338044 HomoloGene3233 IUPHAR: 1357 GeneCards: CYP8B1 Gene
EC number
Species Human Mouse
Entrez 1582 13124
Ensembl ENSG00000180432 ENSMUSG00000050445
UniProt Q9UNU6 O88962
RefSeq (mRNA) NM_004391 NM_010012
RefSeq (protein) NP_004382 NP_034142
Location (UCSC) Chr 3:
42.86 – 42.88 Mb
Chr 9:
121.91 – 121.92 Mb
PubMed search [1] [2]

CYP8B1 (cytochrome P450, family 8, subfamily B, polypeptide 1) also known as sterol 12-alpha-hydroxylase is a protein which in humans is encoded by the CYP8B1 gene.[1]

This gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids.

CYP8B1 is an endoplasmic reticulum membrane protein and catalyzes the conversion of 7 alpha-hydroxy-4-cholesten-3-one into 7-alpha,12-alpha-dihydroxy-4-cholesten-3-one. The balance between these two steroids determines the relative amounts of the two primary bile acids, cholic acid and chenodeoxycholic acid, both of which are secreted in the bile. In the intestine these bile acids affect the solubility of cholesterol and other lipids, promoting their absorption.

CYP8B1 is unique among the cytochrome P450 genes in that it is intronless.[2]


  1. ^ Gåfvels M, Olin M, Chowdhary BP, Raudsepp T, Andersson U, Persson B, Jansson M, Björkhem I, Eggertsen G (March 1999). "Structure and chromosomal assignment of the sterol 12alpha-hydroxylase gene (CYP8B1) in human and mouse: eukaryotic cytochrome P-450 gene devoid of introns". Genomics 56 (2): 184–96. doi:10.1006/geno.1998.5606. PMID 10051404. 
  2. ^ "Entrez Gene: CYP8B1". 

Further reading[edit]

This article incorporates text from the United States National Library of Medicine, which is in the public domain.