Catalyzes the final step of fatty acid oxidation in which acetyl-CoA is released and the CoA ester of a fatty acid two carbons shorter is formed. Involved in the aerobic and anaerobic degradation of long-chain fatty acids. acetyl-CoA + an acyl-CoA = a 3-oxoacyl-CoA + CoA Lipid metabolism; fatty acid beta-oxidation. Heterotetramer of two alpha chains (FadB) and two beta chains (FadA). Repressed by FadR in the absence of LCFAs (fatty acids of, at least, 12 carbon atoms). When LCFAs are present in the medium, they are converted to long-chain acyl-CoAs which bind to FadR resulting in its release from the DNA and thus derepression of the transcription. Belongs to the thiolase-like superfamily. Thiolase family.