MetaCyc Enzyme: 3α-hydroxysteroid dehydrogenase (A-specific)

Gene: Akr1c9 Accession Number: G-10914 (MetaCyc)

Species: Rattus norvegicus

This enzyme is a member of the aldo-keto reductase family. The human ortholog of the gene encoding this enzyme is AKR1C4 (reviewed in [Russell03]). The rat enzyme shares 67% amino acid sequence identity with the four human isoforms of this enzyme (in [Penning04]).

The native enzyme has been purified from rat liver [Penning84, Usui86] and the recombinant enzyme has been overexpressed in Escherichia coli and purified [Pawlowski94]. It has also been expressed in Simian COS7 cells [Usui94]. The recombinant enzyme has been shown to be essentially identical in properties to the native enzyme (in [Penning04]).

The crystal structure of the enzyme has been determined [Bennett97, Bennett96, Hoog94].

The apparent molecular mass was determined to be 34 kDa by SDS-PAGE and 33 kDa by gel filtration chromatography [Penning84].
Note that UniProtKB/Swiss-Prot accession P23457 designates this gene as Akr1c9, although it links to Entrez GeneID: 191574 which names the gene Akr1c14.

Gene Citations: [Lin99, Pawlowski91, Stolz91]

Locations: cytosol

Molecular Weight of Polypeptide: 37.028 kD (from nucleotide sequence), 34.0 kD (experimental) [Penning84 ]

pI: 5.8 [Penning84]

Unification Links: Mint:MINT-4567560 , Pride:P23457 , Protein Model Portal:P23457 , SMR:P23457 , String:P23457 , UniProt:P23457

Relationship Links: Entrez-Nucleotide:PART-OF:AF180334 , InterPro:IN-FAMILY:IPR001395 , InterPro:IN-FAMILY:IPR018170 , InterPro:IN-FAMILY:IPR020471 , InterPro:IN-FAMILY:IPR023210 , Panther:IN-FAMILY:PTHR11732 , PDB:Structure:1afs , PDB:Structure:1lwi , PDB:Structure:1ral , Pfam:IN-FAMILY:PF00248 , Prints:IN-FAMILY:PR00069 , Prosite:IN-FAMILY:PS00062 , Prosite:IN-FAMILY:PS00063 , Prosite:IN-FAMILY:PS00798

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

GO Terms:

Cellular Component: GO:0005829 - cytosol [Penning84]

Created 16-Oct-2008 by Fulcher CA , SRI International

Enzymatic reaction of: NADPH-dehydroascorbate reductase (3α-hydroxysteroid dehydrogenase (A-specific))

L-dehydro-ascorbate + NADPH <=> L-ascorbate + NADP+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.

The reaction is favored in the direction shown.

Alternative Substrates for L-dehydro-ascorbate: 5α-androstane-3,17-dione [Del94 ]

In Pathways: ascorbate recycling (cytosolic)

This enzyme was purified to homogeneity from rat liver cytosol and was shown to have NADPH-dependent dehydroascorbate reductase activity. This activity was strongly inhibited by steroidal and non-steroidal anti-inflammatory drugs. Its identity with 3α-hydroxysteroid dehydrogenase was confirmed by amino acid sequence analysis of cyanogen bromide fragments [Del94].

Kinetic Parameters:

Km (μM)

pH(opt): 6.2 [Del94]

Enzymatic reaction of: 7α-hydroxy-5β-cholestan-3-one 3α-reductase (3α-hydroxysteroid dehydrogenase (A-specific))

5β-cholestane-3α,7α-diol + NAD(P)+ <=> 7α-hydroxy-5β-cholestan-3-one + NAD(P)H + H+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

The reaction is favored in the opposite direction.

In Pathways: bile acid biosynthesis, neutral pathway

Enzymatic reaction of: 7α, 12α-dihydroxy-5β-cholestan-3-one 3α-reductase (3α-hydroxysteroid dehydrogenase (A-specific))

Synonyms: 3α-hydroxysteroid:NAD(P)+ oxidoreductase (A-specifid), 3α-hydroxysteroid/dihydrodiol dehydrogenase

5β-cholestane-3α,7α,12α-triol + NAD(P)+ <=> 7α,12α-dihydroxy-5β-cholestan-3-one + NAD(P)H + H+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

The reaction is favored in the opposite direction.

Alternative Substrates for 7α,12α-dihydroxy-5β-cholestan-3-one: 7α-hydroxy-5β-cholestan-3-one [Usui86 ] , 3-oxo-5β-cholan-24-oate [Usui86 ] , acetophenone [Penning84 ] , duroquinone [Penning84 ] , menadione [Penning84 ] , 4-nitrobenzaldehyde [Penning84 ] , phenanthrenequinone [Penning84 ] , 1,4-benzoquinone [Penning84 ] , 1,4-naphthoquinone [Penning84 ]

In Pathways: bile acid biosynthesis, neutral pathway

This enzyme is designated as EC, rather than EC, because it is an A-specific enzyme that catalyzes the transfer of the 4-pro-R-hydride ion from a nicotinamide cofactor to the carbonyl of an acceptor (in [Penning04a] in [Usui94] and in [Penning04]). Earlier literature used EC, which is now designated as a B-specific enzyme. B-specific enzymes catalyze the transfer of the 4-pro-S-hydride ion.

This reaction is the last step in sterol ring modification during bile acid biosynthesis. It is followed by side chain modification reactions. The reaction involves reduction of the 3-keto group to an α-hydroxyl group (reviewed in [Russell03]). The enzyme also functions in steroid hormone and xenobiotic metabolism, although 3α-hydroxysteroids are the most efficient substrates (in [Pawlowski94].

The reduction of 7α,12α-dihydroxy-5β-cholestan-3-one by this enzyme was demonstrated [Usui86].

The enzyme is inhibited by both nonsteroidal and steroidal anti-inflammatory drugs. Inhibition of the reduction of 7α-hydroxy-5β-cholestan-3-one by indomethacin and dexamethasone was demonstrated [Usui86]. The reduction of phenanthrenequinone and oxidation of androsterone was inhibited by arachidonate and various prostaglandins [Penning84]. The enzyme was not inhibited by D-glucuronate, DL-glyceraldehyde, or glycolaldehyde [Usui86].

Both NADPH and NADH could serve as cofactor, although reactions were more efficient with NADPH [Pawlowski94, Usui86]. A pH optimum of 7.4 was determined for the reduction of 7α-hydroxy-5β-cholestan-3-one [Usui86].

The complete kinetic mechanism of this enzyme has been elucidated using 5α-androstane-3,17-dione and NADPH in the reductive direction and androsterone and NADP+ in the oxidative direction [Cooper07].

Inhibitors (Unknown Mechanism): p-chloromercuribenzoate [Usui86]


Bennett96: Bennett MJ, Schlegel BP, Jez JM, Penning TM, Lewis M (1996). "Structure of 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase complexed with NADP+." Biochemistry 35(33);10702-11. PMID: 8718859

Bennett97: Bennett MJ, Albert RH, Jez JM, Ma H, Penning TM, Lewis M (1997). "Steroid recognition and regulation of hormone action: crystal structure of testosterone and NADP+ bound to 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase." Structure 5(6);799-812. PMID: 9261071

Cooper07: Cooper WC, Jin Y, Penning TM (2007). "Elucidation of a complete kinetic mechanism for a mammalian hydroxysteroid dehydrogenase (HSD) and identification of all enzyme forms on the reaction coordinate: the example of rat liver 3alpha-HSD (AKR1C9)." J Biol Chem 282(46);33484-93. PMID: 17848571

Del94: Del Bello B, Maellaro E, Sugherini L, Santucci A, Comporti M, Casini AF (1994). "Purification of NADPH-dependent dehydroascorbate reductase from rat liver and its identification with 3 alpha-hydroxysteroid dehydrogenase." Biochem J 304 ( Pt 2);385-90. PMID: 7998972

Hoog94: Hoog SS, Pawlowski JE, Alzari PM, Penning TM, Lewis M (1994). "Three-dimensional structure of rat liver 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase: a member of the aldo-keto reductase superfamily." Proc Natl Acad Sci U S A 91(7);2517-21. PMID: 8146147

Lin99: Lin HK, Hung CF, Moore M, Penning TM (1999). "Genomic structure of rat 3alpha-hydroxysteroid/dihydrodiol dehydrogenase (3alpha-HSD/DD, AKR1C9)." J Steroid Biochem Mol Biol 71(1-2);29-39. PMID: 10619355

Pawlowski91: Pawlowski JE, Huizinga M, Penning TM (1991). "Cloning and sequencing of the cDNA for rat liver 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase." J Biol Chem 266(14);8820-5. PMID: 1840601

Pawlowski94: Pawlowski JE, Penning TM (1994). "Overexpression and mutagenesis of the cDNA for rat liver 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase. Role of cysteines and tyrosines in catalysis." J Biol Chem 269(18);13502-10. PMID: 8175784

Penning04: Penning TM, Jin Y, Steckelbroeck S, Lanisnik Rizner T, Lewis M (2004). "Structure-function of human 3 alpha-hydroxysteroid dehydrogenases: genes and proteins." Mol Cell Endocrinol 215(1-2);63-72. PMID: 15026176

Penning04a: Penning TM (2004). "Aldo-keto reductases and formation of polycyclic aromatic hydrocarbon o-quinones." Methods Enzymol 378;31-67. PMID: 15038957

Penning84: Penning TM, Mukharji I, Barrows S, Talalay P (1984). "Purification and properties of a 3 alpha-hydroxysteroid dehydrogenase of rat liver cytosol and its inhibition by anti-inflammatory drugs." Biochem J 222(3);601-11. PMID: 6435601

Russell03: Russell DW (2003). "The enzymes, regulation, and genetics of bile acid synthesis." Annu Rev Biochem 72;137-74. PMID: 12543708

Stolz91: Stolz A, Rahimi-Kiani M, Ameis D, Chan E, Ronk M, Shively JE (1991). "Molecular structure of rat hepatic 3 alpha-hydroxysteroid dehydrogenase. A member of the oxidoreductase gene family." J Biol Chem 266(23);15253-7. PMID: 1714456

Usui86: Usui E, Okuda K (1986). "Identification of 7 alpha,12 alpha-dihydroxy-5 beta-cholestan-3-one 3 alpha-hydroxysteroid dehydrogenase." Biochim Biophys Acta 877(1);158-66. PMID: 3459552

Usui94: Usui E, Okuda K, Kato Y, Noshiro M (1994). "Rat hepatic 3 alpha-hydroxysteroid dehydrogenase: expression of cDNA and physiological function in bile acid biosynthetic pathway." J Biochem 115(2);230-7. PMID: 7515872

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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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