twitter

MetaCyc Enzyme: 3α-hydroxysteroyl-CoA 3-dehydrogenase

Synonyms: BaiA3, 3α-hydroxysteroid dehydrogenase 3, bile acid 7α-dehydroxylase monomer, BaiA1, 3α-hydroxysteroid dehydrogenase 1

Species: Clostridium scindens

Subunit composition of 3α-hydroxysteroyl-CoA 3-dehydrogenase = [BaiA3]4
         3α-hydroxysteroyl-CoA 3-dehydrogenase monomer = BaiA3

Summary:
Clostridium scindens is a human intestinal anaerobic bacterium that possesses an inducible bile acid 7α-dehydroxylase system.

The enzyme encoded by the baiA1 gene was initially thought to encode a bile acid 7α-dehydroxylase [White81, White83]. Following the preparation of an antibody against the enzyme [Paone84], it was purified to homogeneity. N-terminal peptide sequencing and reverse translation was used to identify and clone the baiA1 gene that encodes it [Coleman87]. The molecular weight of the enzyme was estimated by anaerobic Bio-Gel A 1.5 M gel filtration chromatography to be 114 kDa, suggesting the enzyme is a homotetramer [White81].

Subsequent studies have found two additional copies of the gene in the genome. The baiA2 gene is 81% identical to baiA1 (92% amino acid sequence identity), while the baiA3 gene is 100% identical to it [Coleman88, GopalSrivastava90]. All three genes are inducible by bile acids and show highly conserved promoter regions. The physiological significance of the three separate isozymes is unclear.

Despite the early characterization as a bile acid 7α-dehydroxylase, it was later shown that 7α-dehydroxylation is a complex process consisting of many enzymatic activities, and that the three enzymes encoded by the baiA genes are actually 3α-hydroxysteroid dehydrogenases that catalyze one or two reactions in the bile acid 7α-dehydroxylation pathway [Mallonee95].

The baiA1 gene was cloned and overexpressed in Escherichia coli, and the recombinant protein was partially purified and studied [Mallonee95]. At that time it was reported that the enzyme could utilize either NAD+ or NADP+ and catalyzed a reversible reaction. Bile acid-CoA esters were the preferred substrates over free bile acids. The enzyme had very little activity with unconjugated bile acid substrates [Mallonee95].

In a later study the baiA1 gene was cloned with a His6 tag and expressed in Escherichia coli, and the recombinant protein was purified to homogeneity [Bhowmik14]. Biochemical and kinetic characterization showed that the enzyme has relatively similar activities with choloyl-CoA, chenodeoxycholoyl-CoA, deoxycholoyl-CoA, and lithocholoyl-CoA, and that in all cases the reduction reaction was much more efficient at pH 7.3. This preference disappeared at a pH of 8.7.

Unlike previous results, it was shown that the enzyme has a clear preference for NAD over NADP [Bhowmik14].

Molecular Weight of Polypeptide: 26.658 kD (from nucleotide sequence), 27.0 kD (experimental) [Mallonee95]

Molecular Weight of Multimer: 114.0 kD (experimental) [White81]

Isozyme Sequence Similarity:
3α-hydroxysteroid dehydrogenase 2: YES [Comment 1],
3α-hydroxysteroyl-CoA 3-dehydrogenase monomer: YES [Comment 2]

Unification Links: UniProt:P07914

Relationship Links: UniProt:PART-OF:P07914

Gene-Reaction Schematic

Expand/Contract the Schematic connections:

Gene-Reaction Schematic

Credits:
Revised 04-Jun-2010 by Fulcher CA, SRI International
Revised 01-Dec-2015 by Caspi R, SRI International


Enzymatic reaction of: deoxycholoyl-CoA 3-dehydrogenase (3α-hydroxysteroyl-CoA 3-dehydrogenase)

Inferred from experiment

lithocholoyl-CoA + NAD+ ← 3-oxocholan-24-oyl-CoA + NADH + H+

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

The reaction is physiologically favored in the opposite direction.

In Pathways: bile acids degradation

Kinetic Parameters:
Substrate Km (μM) kcat (sec-1) kcat/Km (sec-1 μM-1) Citations
lithocholoyl-CoA 22.0 0.73 0.033 [Bhowmik14]
3-oxocholan-24-oyl-CoA 8.3 0.7 0.084 [Bhowmik14]
NAD+ 17.0 0.3 0.018 [Bhowmik14]

Enzymatic reaction of: deoxycholoyl-CoA 3-dehydrogenase (3α-hydroxysteroyl-CoA 3-dehydrogenase)

Inferred from experiment

12α-hydroxy-3-oxocholan-24-oyl-CoA + NADH + H+ → deoxycholoyl-CoA + NAD+

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the direction of enzyme catalysis.

The reaction is physiologically favored in the direction shown.

In Pathways: bile acids degradation

Kinetic Parameters:
Substrate Km (μM) kcat (sec-1) kcat/Km (sec-1 μM-1) Citations
deoxycholoyl-CoA 16.0 0.87 0.054 [Bhowmik14]
12α-hydroxy-3-oxocholan-24-oyl-CoA 5.6 0.73 0.13 [Bhowmik14]
NAD+ 17.0 0.3 0.018 [Bhowmik14]

Enzymatic reaction of: chenodeoxycholoyl-CoA 3-dehydrogenase (3α-hydroxysteroyl-CoA 3-dehydrogenase)

Inferred from experiment

chenodeoxycholoyl-CoA + NAD+ → 3-oxo-chenodeoxycholoyl-CoA + NADH + H+

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the direction of enzyme catalysis.

The reaction is physiologically favored in the direction shown.

In Pathways: bile acids degradation

Kinetic Parameters:
Substrate Km (μM) kcat (sec-1) kcat/Km (sec-1 μM-1) Citations
chenodeoxycholoyl-CoA 53.0 0.82 0.015 [Bhowmik14]
NAD+ 17.0 0.3 0.018 [Bhowmik14]
3-oxo-chenodeoxycholoyl-CoA 3.3 0.4 0.12 [Bhowmik14]

Enzymatic reaction of: choloyl-CoA 3-dehydrogenase (3α-hydroxysteroyl-CoA 3-dehydrogenase)

Inferred from experiment

choloyl-CoA + NAD+ → 3-oxo-choloyl-CoA + NADH + H+

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the direction of enzyme catalysis.

The reaction is physiologically favored in the direction shown. [Mallonee95]

Alternative Substrates for choloyl-CoA: deoxycholoyl-CoA [Mallonee95]

In Pathways: bile acids degradation

Kinetic Parameters:
Substrate Km (μM) kcat (sec-1) kcat/Km (sec-1 μM-1) Citations
3-oxo-choloyl-CoA 9.1 0.55 0.06 [Bhowmik14]
choloyl-CoA 106.0 1.23 0.012 [Bhowmik14]
NAD+ 0.3 [Bhowmik14]
NAD+ 17.0

References

Bhowmik14: Bhowmik S, Jones DH, Chiu HP, Park IH, Chiu HJ, Axelrod HL, Farr CL, Tien HJ, Agarwalla S, Lesley SA (2014). "Structural and functional characterization of BaiA, an enzyme involved in secondary bile acid synthesis in human gut microbe." Proteins 82(2);216-29. PMID: 23836456

Coleman87: Coleman JP, White WB, Hylemon PB (1987). "Molecular cloning of bile acid 7-dehydroxylase from Eubacterium sp. strain VPI 12708." J Bacteriol 169(4);1516-21. PMID: 3549693

Coleman88: 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

Hylemon98: Hylemon PB, Harder J (1998). "Biotransformation of monoterpenes, bile acids, and other isoprenoids in anaerobic ecosystems." FEMS Microbiol Rev 1998;22(5);475-88. PMID: 9990726

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

Paone84: Paone DA, Hylemon PB (1984). "HPLC purification and preparation of antibodies to cholic acid-inducible polypeptides from Eubacterium sp. V.P.I. 12708." J Lipid Res 25(12);1343-9. PMID: 6442337

White81: White BA, Cacciapuoti AF, Fricke RJ, Whitehead TR, Mosbach EH, Hylemon PB (1981). "Cofactor requiremets for 7 alpha-dehydroxylation of cholic and chenodeoxycholic acid in cell extracts of the intestinal anaerobic bacterium, Eubacterium species V.P.I. 13708." J Lipid Res 22(6);891-8. PMID: 7276750

White83: White BA, Paone DA, Cacciapuoti AF, Fricke RJ, Mosbach EH, Hylemon PB (1983). "Regulation of bile acid 7-dehydroxylase activity by NAD+ and NADH in cell extracts of Eubacterium species V.P.I. 12708." J Lipid Res 24(1);20-7. PMID: 6833878


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 20.0 (software by SRI International) on Fri May 6, 2016, BIOCYC14.