12alpha-hydroxysteroid dehydrogenase

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In enzymology, a 12alpha-hydroxysteroid dehydrogenase (EC 1.1.1.176) is an enzyme that catalyzes the chemical reaction

3alpha,7alpha,12alpha-trihydroxy-5beta-cholanate + NADP⁺ $\rightleftharpoons$ 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholanate + NADPH + H⁺

Thus, the two substrates of this enzyme are 3alpha,7alpha,12alpha-trihydroxy-5beta-cholanate and NADP⁺, whereas its 3 products are 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholanate, NADPH, and H⁺.

This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 12alpha-hydroxysteroid:NADP+ 12-oxidoreductase. Other names in common use include 12alpha-hydroxy steroid dehydrogenase, 12alpha-hydroxy steroid dehydrogenase, NAD+-dependent 12alpha-hydroxysteroid dehydrogenase, and NADP+-12alpha-hydroxysteroid dehydrogenase. This enzyme is involved in a metabolic pathway that degrades bile acids into cholesterol.

[edit] References

IUBMB entry for 1.1.1.176
BRENDA references for 1.1.1.176 (Recommended.)
PubMed references for 1.1.1.176
PubMed Central references for 1.1.1.176
Google Scholar references for 1.1.1.176
MacDonald IA, Mahony DE, Jellet JF, Meier CE (1977). "NAD-dependent 3alpha- and 12alpha-hydroxysteroid dehydrogenase activities from Eubacterium lentum ATCC no. 25559". Biochim. Biophys. Acta. 489: 466–76. PMID 201289.
Mahony DE, Meier CE, Macdonald IA, Holdeman LV (1977). "Bile salt degradation by nonfermentative clostridia". Appl. Environ. Microbiol. 34: 419–23. PMID 921266.