MetaCyc Reaction:

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

EC Number:

Enzymes and Genes:

Clostridium scindens VPI 12708: 3α-hydroxysteroid dehydrogenase 1Inferred from experiment: baiA1
3α-hydroxysteroid dehydrogenase 2Inferred by computational analysis: baiA2
3α-hydroxysteroid dehydrogenase 3Inferred by computational analysis: baiA3
Homo sapiens: 3α hydroxysteroid dehydrogenase III: AKR1C2
retinol dehydrogenase 9: DHRS9

In Pathway: cholate degradation (bacteria, anaerobic)

Note that this reaction equation differs from the official Enzyme Commission reaction equation for this EC number, which can be found here .

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the Enzyme Commission system.

Most BioCyc compounds have been protonated to a reference pH value of 7.3. Please see the PGDB Concepts Guide for more information.

Mass balance status: Balanced.

Enzyme Commission Primary Name: 3α-hydroxysteroid 3-dehydrogenase

Enzyme Commission Synonyms: 3α-hydroxysteroid dehydrogenase, AKR1C4 (gene name), AKR1C2 (gene name), hsdA (gene name)

Standard Gibbs Free Energy (ΔrG in kcal/mol): -10.649414Inferred by computational analysis [Latendresse13]

Enzyme Commission Summary:
The enzyme acts on multiple 3α-hydroxysteroids, such as androsterone and 5 α-dihydrotestosterone. The mammalian enzymes are involved in inactivation of steroid hormones, while the bacterial enzymes are involved in steroid degradation. This entry stands for enzymes whose stereo-specificity with respect to NAD+ or NADP+ is not known. [cf. EC, 3α-hydroxysteroid 3-dehydrogenase (Si-specific) and EC, 3α-hydroxysteroid 3-dehydrogenase (Re-specific)].

Citations: [Deyashiki94, Khanna95, Oppermann96, Mobus98, Nahoum01]

Gene-Reaction Schematic

Gene-Reaction Schematic

Instance reactions of [testosterone + NAD(P)+ → androst-4-ene-3,17-dione + NAD(P)H + H+] (
i3: testosterone + NAD+ = androst-4-ene-3,17-dione + NADH + H+ (

i4: testosterone + NADP+ ← androst-4-ene-3,17-dione + NADPH + H+ (

Instance reactions of [allopregnanolone + NAD(P)+ ↔ 5-α-pregnane-3,20-dione + NAD(P)H + H+] (
i1: allopregnanolone + NAD+ → 5-α-pregnane-3,20-dione + NADH + H+ (1.1.-.-)

i2: allopregnanolone + NADP+ ← 5-α-pregnane-3,20-dione + NADPH + H+ (

Relationship Links: BRENDA:EC:, ENZYME:EC:, IUBMB-ExplorEnz:EC:


Deyashiki94: Deyashiki Y, Ogasawara A, Nakayama T, Nakanishi M, Miyabe Y, Sato K, Hara A (1994). "Molecular cloning of two human liver 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase isoenzymes that are identical with chlordecone reductase and bile-acid binder." Biochem J 299 ( Pt 2);545-52. PMID: 8172617

Khanna95: Khanna M, Qin KN, Wang RW, Cheng KC (1995). "Substrate specificity, gene structure, and tissue-specific distribution of multiple human 3 alpha-hydroxysteroid dehydrogenases." J Biol Chem 270(34);20162-8. PMID: 7650035

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

Mobus98: Mobus E, Maser E (1998). "Molecular cloning, overexpression, and characterization of steroid-inducible 3alpha-hydroxysteroid dehydrogenase/carbonyl reductase from Comamonas testosteroni. A novel member of the short-chain dehydrogenase/reductase superfamily." J Biol Chem 273(47);30888-96. PMID: 9812981

Nahoum01: Nahoum V, Gangloff A, Legrand P, Zhu DW, Cantin L, Zhorov BS, Luu-The V, Labrie F, Breton R, Lin SX (2001). "Structure of the human 3alpha-hydroxysteroid dehydrogenase type 3 in complex with testosterone and NADP at 1.25-A resolution." J Biol Chem 276(45);42091-8. PMID: 11514561

Oppermann96: Oppermann UC, Maser E (1996). "Characterization of a 3 alpha-hydroxysteroid dehydrogenase/carbonyl reductase from the gram-negative bacterium Comamonas testosteroni." Eur J Biochem 241(3);744-9. PMID: 8944761

Report Errors or Provide Feedback
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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