Catalyzes the ligation of CoA on butanoate to produce butanoyl-CoA (PubMed:23300257). Can also use hexanoate, pentanoate and 4-methylpentanoate as substrates with a lower efficiency (PubMed:23300257). ATP + butanoate + CoA = AMP + butanoyl-CoA + diphosphate ATP + CoA + hexanoate = AMP + diphosphate + hexanoyl-CoA ATP + CoA + pentanoate = AMP + diphosphate + pentanoyl-CoA 4-methylpentanoate + ATP + CoA = 4-methylpentanoyl-CoA + AMP + diphosphate A number of isoforms are produced. According to EST sequences. Expressed in roots, leaves, stems, flowers and developing seeds. Belongs to the ATP-dependent AMP-binding enzyme family.