In the production of energy from fats, this is one of the enzymes that catalyzes the last step of the mitochondrial beta-oxidation pathway, an aerobic process breaking down fatty acids into acetyl-CoA. Using free coenzyme A/CoA, catalyzes the thiolytic cleavage of medium- to long-chain unbranched 3-oxoacyl-CoAs into acetyl-CoA and a fatty acyl-CoA shortened by two carbon atoms. Also catalyzes the condensation of two acetyl-CoA molecules into acetoacetyl-CoA and could be involved in the production of ketone bodies. Also displays hydrolase activity on various fatty acyl-CoAs (By similarity). Thereby, could be responsible for the production of acetate in a side reaction to beta-oxidation (By similarity). Abolishes BNIP3-mediated apoptosis and mitochondrial damage (By similarity). acetyl-CoA + an acyl-CoA = a 3-oxoacyl-CoA + CoA 2 acetyl-CoA = acetoacetyl-CoA + CoA acetyl-CoA + H2O = acetate + CoA + H(+) H2O + propanoyl-CoA = CoA + H(+) + propanoate butanoyl-CoA + H2O = butanoate + CoA + H(+) H2O + hexanoyl-CoA = CoA + H(+) + hexanoate H2O + octanoyl-CoA = CoA + H(+) + octanoate decanoyl-CoA + H2O = CoA + decanoate + H(+) dodecanoyl-CoA + H2O = CoA + dodecanoate + H(+) H2O + tetradecanoyl-CoA = CoA + H(+) + tetradecanoate H2O + hexadecanoyl-CoA = CoA + H(+) + hexadecanoate Lipid metabolism; fatty acid beta-oxidation. Homotetramer. Interacts with BNIP3. Belongs to the thiolase-like superfamily. Thiolase family.