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

Basic Information

Enzyme Number

Official Name

cholesterol monooxygenase (side-chain-cleaving)

Name from literature


Pathway from literature

steroid synthesis

Pathway from KEGG

Lipid Metabolism; C21-Steroid hormone metabolism; map00140


Rat (10116)

Genome localization

8q24[29680 ],


A heme-thiolate protein. The reaction proceeds in three stages, with hydroxylation at C-20 and C-22 preceding scission of the side-chain at C-20.

Rate-limiting Description

"Northern and slot blot hybridization analyses revealed that ovarian mRNA levels for cytochrome P450 side-chain cleavage, the rate-limiting enzyme in P synthesis, were markedly reduced in PE rats following hCG stimulation." (10964264)

"Regulation of steroidogenesis in classic endocrine tissues is mediated by transcriptional regulation of the P450scc gene, which encodes the first and rate-limiting cholesterol side-chain cleavage enzyme." (8584034)

"In the present study, we evaluate the effect of IGF-I on the gene expression and protein levels of steroidogenic acute regulatory protein (StAR), the rate-limiting step in steroidogenesis." (9666348)

"StAR mediates the rate-limiting step of steroidogenesis, which is the transfer of cholesterol to the inner mitochondrial membrane." (10619400)

"Here, we found that P450scc, the rate-limiting enzyme in steroid synthesis, is upregulated in hippocampal glia during the latent period after pilocarpine-induced SE in rats." (16780839)

"Herein, we demonstrate that culturing the aged cells with dibutyryl cAMP, a membrane-permeable cAMP agonist that bypasses the LH receptor-adenlyly cyclase cascade, restores testosterone production to levels comparable to those of young cells and also restores steroidogenic acute regulatory protein and P450scc, the proteins involved in the rate-limiting steps of steroidogenesis." (15231695)

"P450scc is the key enzyme catalyzing the conversion of cholesterol (CHOL) into PREG, the rate-limiting step in the biosynthesis of all classes of steroids." (16632873)

"These results support the hypothesis that NO inhibits the rate-limiting enzyme in steroidogenesis independent of GC-S activation." (12242026)

"In these studies, several structurally related phthalates (0-200 microM) and Wy-14,643 (0-100 microM) were compared to MEHP for their effects on granulosa cell estradiol production and transcript levels of cytochrome P450 enzyme CYP 19, also known as aromatase (P450arom), the rate-limiting enzyme in the conversion of androgens to estrogens." (11312650)

"The mRNA levels of Cyp11a - a rate-limiting enzyme in testosterone synthesis - positively correlated with the menaquinone-4 (MK-4) concentration in the testis." (16844298)

"However, because P450scc is reduced in old Leydig cells, the reaction catalyzed by this enzyme would be rate-limiting under circumstances in which saturating amounts of cholesterol entered the mitochondria." (11191081)

"There are two main regulatory sites of aldosterone biosynthesis, the early rate-limiting step by the P450scc and the final steps by the P450aldo." (9888540)

Regulatory Information

Upstream transcription factor


Regulatory type


transcriptional factor;PGC-1alpha(83516)

"ERalpha interaction with transcription coregulators, histone acetylases (CBP/SRC-1), and PGC-1alpha is crucial to FSH and TGFbeta1-up-regulated expression of Hsd3b and Cyp11a1, and, thus, progesterone production in rat ovarian granulosa cells." (18511507)

Gene ontology

Gene ontology

GO:0031966 (C) mitochondrial membrane [P14137 ];
GO:0008386 (F) cholesterol monooxygenase (side-chain-cleav... [P14137 ];
GO:0006700 (P) C21-steroid hormone biosynthetic process [P14137 ];
GO:0008203 (P) cholesterol metabolic process [P14137 ];
GO:0020037 (F) heme binding [P14137 ];
GO:0005506 (F) iron ion binding [P14137 ];
GO:0009055 (F) electron carrier activity [P14137 ];
GO:0055114 (P) oxidation reduction [P14137 ];

Subcellular localization


mitochondrion [P14137 ];




Entrez Gene


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