Involved in the final steps of cholesterol and steroid degradation (PubMed:28377529). Opens the last steroid ring of cholesterol by catalyzing the hydrolysis of (3E)-2-(2-carboxylatoethyl)-3-methyl-6-oxocyclohex-1-ene-1-carboxyl-CoA (COCHEA-CoA) to 6-methyl-3,7-dioxodecanedioyl-CoA (MeDODA-CoA) (PubMed:29581275). (3E)-2-(2-carboxylatoethyl)-3-methyl-6-oxocyclohex-1-ene-1-carboxyl-CoA + H2O = 6-methyl-3,7-dioxodecanedioyl-CoA Steroid metabolism; cholesterol degradation. Heterotetramer composed of 2 IpdA subunits and 2 IpdB subunits. IpdAB double deletion mutant does not grow on cholesterol, but grows as the wild-type on glycerol. In the presence of cholesterol, ipdAB double deletion mutant accumulates COCHEA-CoA. Double mutant does not survive in macrophages and displays severely depleted CoASH levels that correlate with a cholesterol-dependent toxicity. Belongs to the 3-oxoacid CoA-transferase subunit A family.