Steroid 21-monooxygenase Identifiers EC number 1.14.99.10 CAS number 9029-68-9 IntEnz IntEnz view BRENDA BRENDA entry ExPASy NiceZyme view KEGG KEGG entry MetaCyc metabolic pathway PRIAM profile PDB structures Gene Ontology AmiGO / EGO Search PMC articles PubMed articles

edit Cytochrome P450, family 21, subfamily A, polypeptide 2 Identifiers Symbols CYP21A2; CPS1; CA21H; CAH1; CYP21; CYP21B; MGC150536; MGC150537; P450c21B External IDs OMIM: 201910 MGI: 88591 HomoloGene: 68063 GeneCards: CYP21A2 Gene 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 Species Human Mouse Entrez 1589 13079 Ensembl ENSG00000168482 ENSMUSG00000024365 UniProt P08686 A0JP50 RefSeq (mRNA) NM_000500 NM_009995 RefSeq (protein) NP_000491 NP_034125 Location (UCSC) Chr c6_COX: 32.1 - 32.1 Mb Chr 17: 34.41 - 34.41 Mb PubMed search [1] [2]

Steroid 21-hydroxylase is a cytochrome P450 enzyme that is involved with the biosynthesis of the steroid hormones aldosterone and cortisol.^[1]

In humans, 21-Hydroxylase is encoded by the gene CYP21B.^[2]

[edit] Names and classification

21-Hydroxylase is also called steroid 21-monooxygenase, 21α-Hydroxylase, and, less commonly 21β-Hydroxylase.

[edit] Function

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. This protein localizes to the endoplasmic reticulum and hydroxylates steroids at the 21 position. Its activity is required for the synthesis of steroid hormones including cortisol and aldosterone.^[3]

[edit] Reaction

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

Progesterone   11-deoxycorticosterone   Steroid numbering - #21 is near center top

[edit] Pathway

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

Corticosteroid biosynthetic pathway in the rat.

[edit] 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.^[3]

[edit] References

[edit] Further reading

[edit] External links

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

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