Catalyzes the initial reaction in intramitochondrial fatty acid synthesis, by activating malonate and methylmalonate, but not acetate, into their respective CoA thioester (PubMed:21846720, PubMed:21841779). May have some preference toward very-long-chain substrates (PubMed:17762044). ATP + CoA + tetracosanoate = AMP + diphosphate + tetracosanoyl-CoA ATP + CoA + malonate = AMP + diphosphate + malonyl-CoA The disease is caused by variants affecting the gene represented in this entry. Belongs to the ATP-dependent AMP-binding enzyme family. Aberrant splicing.