MetaCyc Reaction:

Superclasses: Reactions Classified By Conversion TypeSimple ReactionsChemical Reactions
Reactions Classified By SubstrateSmall-Molecule Reactions

EC Number:

Enzymes and Genes:

Homo sapiens: steroid 17-alpha-hydroxylase/17,20 lyase: CYP17A1

Supersedes EC numbers:,

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the direction in which it was curated.

Mass balance status: Balanced.

Enzyme Commission Primary Name: steroid 17α-monooxygenase

Enzyme Commission Synonyms: steroid 17α-hydroxylase, cytochrome P-45017α, cytochrome P-450 (P-45017α,lyase), 17α-hydroxylase-C17,20 lyase, CYP17, CYP17A1 (gene name)

Taxonomic Range: Metazoa

Standard Gibbs Free Energy (ΔrG in kcal/mol): -33.78675Inferred by computational analysis [Latendresse13]

Enzyme Commission Summary:
Requires NADPH and EC, NADPH--hemoprotein reductase. A microsomal hemeprotein that catalyses two independent reactions at the same active site - the 17α-hydroxylation of pregnenolone and progesterone, which is part of glucocorticoid hormones biosynthesis, and the conversion of the 17α-hydroxylated products via a 17,20-lyase reaction to form androstenedione and dehydroepiandrosterone, leading to sex hormone biosynthesis ( EC, 7α-hydroxyprogesterone aldolase). The ratio of the 17α-hydroxylase and 17,20-lyase activities is an important factor in determining the directions of steroid hormone biosynthesis towards biosynthesis of glucocorticoid or sex hormones.

Citations: [Lynn58, Yoshida80, Gilep03, Kolar07, Pechurskaya08]

Gene-Reaction Schematic

Gene-Reaction Schematic

Unification Links: KEGG:R02131

Relationship Links: BRENDA:EC:, ENZYME:EC:, IUBMB-ExplorEnz:EC:, UniProt:RELATED-TO:P05093, UniProt:RELATED-TO:P05185, UniProt:RELATED-TO:P11715, UniProt:RELATED-TO:P12394, UniProt:RELATED-TO:P19100, UniProt:RELATED-TO:P27786, UniProt:RELATED-TO:P30437, UniProt:RELATED-TO:Q64410, UniProt:RELATED-TO:Q92113


Gilep03: Gilep AA, Estabrook RW, Usanov SA (2003). "Molecular cloning and heterologous expression in E. coli of cytochrome P45017alpha. Comparison of structural and functional properties of substrate-specific cytochromes P450 from different species." Biochemistry (Mosc) 68(1);86-98. PMID: 12693981

Kolar07: Kolar NW, Swart AC, Mason JI, Swart P (2007). "Functional expression and characterisation of human cytochrome P45017alpha in Pichia pastoris." J Biotechnol 129(4);635-44. PMID: 17386955

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

Lynn58: Lynn WS, Brown RH (1958). "The conversion of progesterone to androgens by testes." J Biol Chem 232(2);1015-30. PMID: 13549484

Pechurskaya08: Pechurskaya TA, Lukashevich OP, Gilep AA, Usanov SA (2008). "Engineering, expression, and purification of "soluble" human cytochrome P45017alpha and its functional characterization." Biochemistry (Mosc) 73(7);806-11. PMID: 18707589

Yoshida80: Yoshida KI, Oshima H, Troen P (1980). "Studies of the human testis. XIII. Properties of nicotinamide adenine dinucleotide (reduced form)-linked 17 alpha-hydroxylation." J Clin Endocrinol Metab 50(5);895-9. PMID: 6966286

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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