MetaCyc Enzyme: 3β-hydroxysteroid dehydrogenase

Species: Blautia producta K 2/25.1

The gene encoding this 3β-hydroxysteroid dehydrogenase has not been identified and its subunit structure has not been determined. The native apparent molecular mass was determined by gel filtration chromatography to be 132 kDa. The enzyme was characterized in cell extracts of anaerobically grown Blautia producta K 2/25.1 (previously known as Peptostreptococcus productus strain K 2/25.1), a human intestinal bacterium. The enzyme was constitutively produced and was suggested to be membrane-bound, due to a higher specific activity associated with a detergent-solubilized membrane fraction. In addition, a distinct, constitutively produced 3α-hydroxysteroid dehydrogenase was also characterized in this organism, as well as a NADP-dependent 7β-hydroxysteroid dehydrogenase [Edenharder89].

Bacterial 3α and 3β hydroxysteroid dehydrogenases (HSDHs) catalyze stereo-specific redox reactions that interconvert 3-oxo bile acids to 3α-hydroxy or 3β-hydroxy bile acids. They have been characterized in both intestinal and non-intestinal bacteria. The 3α-HSDHs generally require NAD(H) and 3β-HSDHs generally require NADP(H), although exceptions to both cases exist. These enzymes are generally constitutively expressed, again with some exceptions such as the primary bile acid-inducible 3α-hydroxysteroid dehydrogenase 1 (reviewed in [Ridlon06]).

Gene-Reaction Schematic

Gene-Reaction Schematic

Created 14-Jun-2010 by Fulcher CA, SRI International

Enzymatic reaction of: 3-dehydrocholate reductase (3β-hydroxysteroid dehydrogenase)

Inferred from experiment

3-dehydrocholate + NADH + H+ → isocholate + NAD+

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the direction in which it was curated.

The reaction is favored in the direction shown.

In Pathways: glycocholate metabolism (bacteria)

This constitutively produced enzyme activity was demonstrated in extracts of Blautia producta K 2/25.1 (Peptostreptococcus productus strain K 2/25.1. Addition of 3-keto bile acids to the growth media reduced the specific activity The enzyme was also assayed using 3-keto-12α-hydroxy-5β-cholanoate as substrate. Reaction products were identified by GLC and TLC. The enzyme used NADH and could not use NADPH as coenzyme. Substrate inhibition was observed with excess substrate over the optimum concentration of 0.1-0.25 mM [Edenharder89].

pH(opt): 9.5 [Edenharder89]


Edenharder89: Edenharder R, Pfutzner A, Hammann R (1989). "Characterization of NAD-dependent 3 alpha- and 3 beta-hydroxysteroid dehydrogenase and of NADP-dependent 7 beta-hydroxysteroid dehydrogenase from Peptostreptococcus productus." Biochim Biophys Acta 1004(2);230-8. PMID: 2752021

Ridlon06: Ridlon JM, Kang DJ, Hylemon PB (2006). "Bile salt biotransformations by human intestinal bacteria." J Lipid Res 47(2);241-59. PMID: 16299351

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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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