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. Responsible for the synthesis of short- and branched-chain acylcarnitines. Active towards some branched-chain amino acid oxidation pathway (BCAAO) intermediates. Trans-2-enoyl-CoAs and 2-methylacyl-CoAs are poor substrates. (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. Belongs to the carnitine/choline acetyltransferase family.