In enzymology, a sterol-4alpha-carboxylate 3-dehydrogenase (decarboxylating) () is an enzyme that catalyzes the chemical reaction
The 3 substrates of this enzyme are 3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate, NAD<sup>+</sup>, and NADP<sup>+</sup>, whereas its 4 products are 4alpha-methyl-5alpha-cholest-7-en-3-one, CO<sub>2</sub>, NADH, and NADPH.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD<sup>+</sup> or NADP<sup>+</sup> as acceptor. The systematic name of this enzyme class is 3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate:NAD(P)<sup>+</sup> 3-oxidoreductase (decarboxylating). Other names in common use include 3beta-hydroxy-4beta-methylcholestenecarboxylate 3-dehydrogenase, (decarboxylating), 3beta-hydroxy-4beta-methylcholestenoate dehydrogenase, 3beta-hydroxy-4beta-methylcholestenoate dehydrogenase, and sterol 4alpha-carboxylic decarboxylase. This enzyme participates in biosynthesis of steroids.