Mitochondrial acetyl-CoA acetyltransferase that catalyzes both the formation and degradation of acetoacetyl-CoA (By similarity). Seems not to be involved in ergosterol biosynthesis (By similarity). Plays an important role in growth, morphogenesis and maintaining mitochondrial function including the response to oxidative stresses (By similarity). 2 acetyl-CoA = acetoacetyl-CoA + CoA Homotetramer. Belongs to the thiolase-like superfamily. Thiolase family.