Center for Bioinformatics
Oxidoreductases | Transferases | Hydrolases | Lyases | Isomerases | Ligases

Basic Information

Enzyme Number

Official Name

steroid 17alpha-monooxygenase

Name from literature


Pathway from literature

androgen biosynthesis

Pathway from KEGG

Lipid Metabolism; C21-Steroid hormone metabolism; map00140


Human (9606)

Genome localization

10q24.3[1586 ],


Requires NAD(P)H and P-450.

Rate-limiting Description

"Therefore, we determined the effects of estrogen treatment at midgestation and removal of estrogen action near term on the specific activity of the rate-limiting enzymes delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta HSD) and 17-hydroxylase-17,20-lyase (17 alpha-OHase)." (2019257)

"The most likely cause of the excessive androgen secretion by both glands seems to be abnormal regulation (dysregulation) of the 17-hydroxylase and 17,20-lyase activities of P-450c17, the rate-limiting step in androgen biosynthesis." (10352919)

Regulatory Information

Upstream transcription factor


Regulatory type


signal pathway;

"activation of protein phosphatase(s) is essential for cAMP-dependent transcription of human CYP17" (11956159)

signal pathway;

"enhancement of transcription by cAMP-dependent protein kinase via MKP-1 activation in human adrenocortical cells" (12506119)

transcriptional factor;SF-1(2516)

"A dual-specificity phosphatase, possibly MKP-1, is essential for enhancing hCYP17 transcription in adrenal cortex by desphosphorylating of SF-1, thereby increasing the binding affinity of SF-1, p54nrb, and PSF for hCYP17 promoter." (12530662)

transcriptional factor;SREBP1(6720)

"there is a role for sphingolipid metabolism and SREBP1 in ACTH-dependent CYP17 regulation and steroidogenesis" (16306078)


"PKA 1) induces metabolic changes in the adrenal cortex and 2) phosphorylates CtBP1 and 2 proteins, particularly CtBP1 at T144, resulting in CtBP protein partnering and ACTH-dependent CYP17 transcription" (18184656)



Gene ontology

Gene ontology

GO:0006700 (P) C21-steroid hormone biosynthetic process [P05093 ];
GO:0019825 (F) oxygen binding [P05093 ];
GO:0020037 (F) heme binding [P05093 ];
GO:0005506 (F) iron ion binding [P05093 ];
GO:0005789 (C) endoplasmic reticulum membrane [P05093 ];
GO:0004508 (F) steroid 17-alpha-monooxygenase activity [P05093 ];
GO:0009055 (F) electron carrier activity [P05093 ];
GO:0055114 (P) oxidation reduction [P05093 ];
GO:0007548 (P) sex differentiation [P05093 ];

Subcellular localization


membrane [P05093 ];

Disease relevance


Defects in CYP17A1 are the cause of adrenal hyperplasia type 5 (AH5) [MIM:202110]. AH5 is a form of congenital adrenal hyperplasia, a common recessive disease due to defective synthesis of cortisol. Congenital adrenal hyperplasia is characterized by androgen excess leading to ambiguous genitalia in affected females, rapid somatic growth during childhood in both sexes with premature closure of the epiphyses and short adult stature. Four clinical types: "salt wasting" (SW, the most severe type), "simple virilizing" (SV, less severely affected patients), with normal aldosterone biosynthesis, "non-classic form" or late onset (NC or LOAH), and "cryptic" (asymptomatic) [P05093 ];




Entrez Gene




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  Last Modified: 2009-03-24  
  Design by Zhao Min