12alpha-hydroxysteroid dehydrogenase

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

3alpha,7alpha,12alpha-trihydroxy-5beta-cholanate + NADP+ 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.


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  • 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&ndash, 76. PMID 201289.
  • Mahony DE, Meier CE, Macdonald IA, Holdeman LV (1977). "Bile salt degradation by nonfermentative clostridia". Appl. Environ. Microbiol. 34: 419&ndash, 23. PMID 921266.

External links

The CAS registry number for this enzyme class is 61642-40-8.

Gene Ontology (GO) codes