21-Hydroxylase

Cytochrome P450, family 21, subfamily A, polypeptide 2
Identifiers
Symbol(s)	CYP21A2; CPS1; CA21H; CAH1; CYP21; CYP21B; MGC150536; MGC150537; P450c21B
External IDs	OMIM: 201910 MGI: 88591 Homologene: 68063
Gene ontology Molecular Function: • monooxygenase activity • steroid 21-monooxygenase activity • steroid binding • iron ion binding • lipid binding • oxygen binding • heme binding • metal ion binding Cellular Component: • endoplasmic reticulum • microsome • membrane Biological Process: • electron transport • C21-steroid hormone biosynthetic process
RNA expression pattern
More reference expression data
Orthologs
	Human	Mouse
Entrez	1589	13079
Ensembl	ENSG00000168482	ENSMUSG00000024365
Uniprot	P08686	A0JP50
Refseq	NM_000500 (mRNA) NP_000491 (protein)	NM_009995 (mRNA) NP_034125 (protein)
Location	Chr c6_COX: 32.1 - 32.1 Mb	Chr 17: 34.41 - 34.41 Mb
Pubmed search	[1]	[2]

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Overview

Steroid 21-hydroxylase (or steroid 21-monooxygenase or 21α-Hydroxylase; EC 1.14.99.10) is a cytochrome P450 enzyme which is involved with the biosynthesis of the steroid hormones aldosterone and cortisol.

The CAS number is 9029-68-9.

21-Hydroxylase is encoded by the gene CYP21B.

Reaction

It catalyses the hydroxylation of the carbon atom 21 in steroids (adding an "–OH"), which is necessary with the formation of these hormones.

• 

  Progesterone

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  11-deoxycorticosterone

• 

  Steroid numbering - #21 is near center top

Pathway

Corticosteroid biosynthetic pathway in rat

Steroidogenesis, showing both reactions of 21-Hydroxylase at center top.

Clinical significance

A defect within the CYP21B gene causes a disturbance of the development of the enzyme, which leads to congenital adrenal hyperplasia due to 21-hydroxylase deficiency. A related pseudogene is located near this gene; gene conversion events involving the functional gene and the pseudogene are thought account for many cases of steroid 21-hydroxylase deficiency.

Further reading

• White PC, Tusie-Luna MT, New MI, Speiser PW (1994). "Mutations in steroid 21-hydroxylase (CYP21).". Hum. Mutat. 3 (4): 373-8. doi:10.1002/humu.1380030408. PMID 8081391.
• Helmberg A (1993). "Twin genes and endocrine disease: CYP21 and CYP11B genes.". Acta Endocrinol. 129 (2): 97-108. PMID 8372604.
• de-Araujo M, Sanches MR, Suzuki LA, et al. (1996). "Molecular analysis of CYP21 and C4 genes in Brazilian families with the classical form of steroid 21-hydroxylase deficiency.". Braz. J. Med. Biol. Res. 29 (1): 1-13. PMID 8731325.
• Yu CY (1999). "Molecular genetics of the human MHC complement gene cluster.". Exp. Clin. Immunogenet. 15 (4): 213-30. PMID 10072631.
• Forest MG, Tardy V, Nicolino M, et al. (2005). "21-Hydroxylase deficiency: an exemplary model of the contribution of molecular biology in the understanding and management of the disease.". Ann. Endocrinol. (Paris) 66 (3): 225-32. PMID 15988383.

External links

• Synthesis of Desoxycorticosterone from Progesterone through 21-Hydroxylase (Image)
• MeSH Steroid+21-Hydroxylase