Involved in the final steps of cholesterol and steroid degradation (PubMed:28377529). Probably catalyzes the introduction of a double bound into the C ring of 5OH-HIC-CoA, leading to the formation of (5R,7aS)-5-hydroxy-7a-methyl-1-oxo-3,5,6,7-tetrahydro-2H-indene-4-carboxyl-CoA (Probable). (3aS,4S,5R,7aS)-5-hydroxy-7a-methyl-1-oxo-octahydro-1H-indene-4-carboxyl-CoA + NAD(+) = (5R,7aS)-5-hydroxy-7a-methyl-1-oxo-2,3,5,6,7,7a-hexahydro-1H-indene-carboxyl-CoA + H(+) + NADH Requires the presence of IpdF. Steroid metabolism; cholesterol degradation. Deletion mutant does not grow on cholesterol, but grows as the wild-type on glycerol. In the presence of cholesterol, disruption mutant accumulates 5OH-HIC-CoA. Belongs to the nitronate monooxygenase family.