Updated BioCyc iOS App now
available in iTunes store
Updated BioCyc iOS App now
available in iTunes store
Updated BioCyc iOS App now
available in iTunes store
Updated BioCyc iOS App now
available in iTunes store
Updated BioCyc iOS App now
available in iTunes store

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 [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
Page generated by Pathway Tools version 19.5 (software by SRI International) on Wed May 4, 2016, biocyc14.