Catalyzes the synthesis of acetyl-CoA from short-chain fatty acids (By similarity). Propionate is the preferred substrate but can also utilize acetate and butyrate with a much lower affinity. acetate + ATP + CoA = acetyl-CoA + AMP + diphosphate ATP + CoA + propanoate = AMP + diphosphate + propanoyl-CoA ATP + butanoate + CoA = AMP + butanoyl-CoA + diphosphate Belongs to the ATP-dependent AMP-binding enzyme family.