Sterol 4alpha carboxylate 3 dehydrogenase (decarboxylating)

In enzymology, a sterol-4alpha-carboxylate 3-dehydrogenase (decarboxylating) (EC 1.1.1.170) is an enzyme that catalyzes the chemical reaction

3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate + NAD(P)⁺ ⇌ 4alpha-methyl-5alpha-cholest-7-en-3-one + CO₂ + NAD(P)H

The 3 substrates of this enzyme are 3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate, NAD⁺, and NADP⁺, whereas its 4 products are 4alpha-methyl-5alpha-cholest-7-en-3-one, CO₂, NADH, and NADPH.

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 3beta-hydroxy-4beta-methyl-5alpha-cholest-7-ene-4alpha-carboxylate:NAD(P)⁺ 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.