|Gene:||baiA1||Accession Number: G-140 (MetaCyc)|
Species: Clostridium scindens VPI 12708
The experimentally determined subunit structure of this enzyme has not been reported.
In Clostridium scindens VPI 12708 (previously known as Eubacterium sp. strain VPI 12708) three separate genes, baiA1, baiA2 and baiA3 encode 3α-hydroxysteroid dehydrogenases that catalyze the second reaction in the bile acid 7α-dehydroxylation pathway. The physiological significance of the three separate isozymes is unclear. Genes baiA1 and baiA3 are monocistronic, while gene baiA2 is part of a bile acid-inducible bai operon in this organism. Genes baiA1 and baiA3 are identical in nucleotide sequence in the coding region, while gene baiA2 shows 81% nucleotide sequence identity with baiA1 and baiA3. It has been suggested that baiA1 and baiA3 are the result of a stably maintained gene duplication in this organism [GopalSrivastava90]. All three genes are inducible by bile acids and show highly conserved promoter regions At the amino acid sequence level, BaiA1 and BaiA3 are 100% identical. BaiA1 and BaiA2 have 92% amino acid sequence identity [Mallonee95, Hylemon98, Mallonee90].
Gene Citations: [Coleman88a]
Molecular Weight of Polypeptide: 26.658 kD (from nucleotide sequence), 27.0 kD (experimental) [Mallonee95 ]
Unification Links: Entrez-Nucleotide:M19654
Relationship Links: UniProt:PART-OF:P07914
Enzymatic reaction of: choloyl-CoA dehydrogenase (3α-hydroxysteroid dehydrogenase 1)
Synonyms: 3α-HSDH, 3α-hydroxysteroid dehydrogenase
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction of enzyme catalysis.
This reaction is reversible. [Mallonee95]
In Pathways: cholate degradation (bacteria, anaerobic)
The enzyme could utilize either NAD+ or NADP+ and the reaction was reversible. The choloyl-CoA conjugate was the preferred substrate over cholate. The enzyme had very little activity with unconjugated bile acid substrates. choloyl-CoA was the preferred substrate over deoxycholyl-CoA which had 75% relative activity. With NADP+ as cofactor, the following could not serve as substrate: cholate, chenodeoxycholate, deoxycholate, glycocholate, taurocholate and ursodeoxycholate [Mallonee95].
Coleman88a: Coleman JP, White WB, Lijewski M, Hylemon PB (1988). "Nucleotide sequence and regulation of a gene involved in bile acid 7-dehydroxylation by Eubacterium sp. strain VPI 12708." J Bacteriol 170(5);2070-7. PMID: 2834320
GopalSrivastava90: Gopal-Srivastava R, Mallonee DH, White WB, Hylemon PB (1990). "Multiple copies of a bile acid-inducible gene in Eubacterium sp. strain VPI 12708." J Bacteriol 172(8);4420-6. PMID: 2376563
Mallonee95: Mallonee DH, Lijewski MA, Hylemon PB (1995). "Expression in Escherichia coli and characterization of a bile acid-inducible 3 alpha-hydroxysteroid dehydrogenase from Eubacterium sp. strain VPI 12708." Curr Microbiol 1995;30(5);259-63. PMID: 7766153
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