Involved in the beta-oxidation of the cholesterol side chain. It is important for utilization of cholesterol as a sole carbon source in vitro and for full virulence in the chronic stage of mouse lung infection. Catalyzes the thiolysis of 3,22-dioxochol-4-en-24-oyl-CoA to yield 3-oxo-4-pregnene-20-carboxyl-CoA (3-OPC-CoA) and acetyl-CoA. Also able to use acetoacetyl-CoA (AcAcCoA) as substrate