Involved in the final steps of cholesterol and steroid degradation. 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). (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. Belongs to the 3-oxoacid CoA-transferase subunit B family.