3beta-hydroxysteroid-dehydrogenase/decarboxylase involved in sterol synthesis (PubMed:16835224). Catalyzes the formation of 3-oxosteroids from 3beta-hydroxysteroids-4alpha-carboxylate (PubMed:16835224). Involved in the regulation of inflorescence internodes and leaves growth, probably by affecting auxin transporter activity possibly by altering sterol composition in the membranes (PubMed:22673766). a 3beta-hydroxysteroid-4alpha-carboxylate + NAD(+) = a 3-oxosteroid + CO2 + NADH 4alpha-carboxy-4beta,14alpha-dimethyl-9beta,19-cyclo-5alpha-ergost-24(24(1))-en-3beta-ol + NAD(+) = CO2 + cycloeucalenone + NADH Steroid biosynthesis; zymosterol biosynthesis; zymosterol from lanosterol: step 4/6. The RETICULON domain is partial in comparison with the other paralogs. No noticeable phenotype. May be due to a competing acceptor splice site. Belongs to the 3-beta-HSD family. Lacks one transmembrane, which is a conserved feature of the family. Extended N-terminus. Extended N-terminus.