In enzymology, a 3alpha,7alpha,12alpha-trihydroxycholestan-26-al 26-oxidoreductase is an enzyme that catalyzes the chemical reaction: (25R)-3alpha,7alpha,12alpha-trihydroxy-5beta-cholestan-26-al + NAD+ + H2O (25R)-3alpha,7alpha,12alpha-trihydroxy-5beta-cholestan-26-oate + NADH + 2 H+ The 3 substrates of this enzyme are (25R)-3alpha,7alpha,12alpha-trihydroxy-5beta-cholestan-26-al, NAD+, and H2O, whereas its 2 products are (25R)-3alpha,7alpha,12alpha-trihydroxy-5beta-cholestan-26-oate, NADH, and H+. This enzyme participates in bile acid biosynthesis. Nomenclature This enzyme belongs to the family of oxidoreductases, specifically those acting on the aldehyde or oxo group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (25R)-3alpha,7alpha,12alpha-trihydroxy-5beta-cholestan-26-al:NAD+ 26-oxidoreductase. Other names in common use include: cholestanetriol-26-al 26-dehydrogenase, 3alpha,7alpha,12alpha-trihydroxy-5beta-cholestan-26-al, dehydrogenase, trihydroxydeoxycoprostanal dehydrogenase, THAL-NAD oxidoreductase, 3alpha,7alpha,12alpha-trihydroxy-5beta-cholestan-26-al:NAD+, and 26-oxidoreductase. References EC 1.2.1 NADH-dependent enzymes Enzymes of unknown structure