Stereo-specific NAD(H)-dependent 3-oxo-delta4-cholenoic acid oxidoreductase involved in bile acid 7alpha-dehydroxylation. 7alpha,12alpha-dihydroxy-3-oxochol-24-oyl-CoA + NAD(+) = 7alpha,12alpha-dihydroxy-3-oxochol-4-en-24-oyl-CoA + H(+) + NADH 7alpha-hydroxy-3-oxochol-24-oyl-CoA + NAD(+) = 7alpha-hydroxy-3-oxochol-4-en-24-oyl-CoA + H(+) + NADH Lipid metabolism; bile acid degradation. In the N-terminal section; belongs to the NADH:flavin oxidoreductase/NADH oxidase family. Was originally thought to be the product of two separate ORFs, baiC and baiD.