Catalyzes the reversible transfer of acyl groups from carnitine to coenzyme A (CoA) and regulates the acyl-CoA/CoA ratio. Also plays a crucial role in the transport of fatty acids for beta-oxidation (PubMed:15099582, PubMed:29395073). Responsible for the synthesis of short- and branched-chain acylcarnitines (PubMed:23485643). Active towards some branched-chain amino acid oxidation pathway (BCAAO) intermediates (PubMed:23485643). Trans-2-enoyl-CoAs and 2-methylacyl-CoAs are poor substrates (PubMed:23485643). (R)-carnitine + acetyl-CoA = CoA + O-acetyl-(R)-carnitine (R)-carnitine + propanoyl-CoA = CoA + O-propanoyl-(R)-carnitine (R)-carnitine + butanoyl-CoA = CoA + O-butanoyl-(R)-carnitine (R)-carnitine + hexanoyl-CoA = CoA + O-hexanoyl-(R)-carnitine (R)-carnitine + octanoyl-CoA = CoA + O-octanoyl-(R)-carnitine (R)-carnitine + decanoyl-CoA = CoA + O-decanoyl-(R)-carnitine (R)-carnitine + 3-methylbutanoyl-CoA = CoA + O-3-methylbutanoyl-(R)-carnitine (R)-carnitine + 2-methylpropanoyl-CoA = CoA + O-isobutanoyl-(R)-carnitine (R)-carnitine + 2-methylbutanoyl-CoA = CoA + O-2-methylbutanoyl-(R)-carnitine (R)-carnitine + acetoacetyl-CoA = CoA + O-3-oxobutanoyl-(R)-carnitine (R)-carnitine + 3-hydroxybutanoyl-CoA = CoA + O-3-hydroxybutanoyl-(R)-carnitine (R)-carnitine + 4,8-dimethylnonanoyl-CoA = CoA + O-4,8-dimethylnonanoyl-(R)-carnitine (R)-carnitine + 2,6-dimethylheptanoyl-CoA = CoA + O-2,6-dimethylheptanoyl-(R)-carnitine Monomer. Mostly in skeletal muscle, less in heart, liver and pancreas, only weakly detectable in brain, placenta, lung and kidney. The disease is caused by variants affecting the gene represented in this entry. Belongs to the carnitine/choline acetyltransferase family.