Involved in the intramitochondrial synthesis of acylcarnitines from accumulated acyl-CoA metabolites. Reconverts acylcarnitines back into the respective acyl-CoA esters that can then undergo beta-oxidation, an essential step for the mitochondrial uptake of long-chain fatty acids and their subsequent beta-oxidation in the mitochondrion. Active with medium (C8-C12) and long-chain (C14-C18) acyl-CoA esters. (R)-carnitine + hexadecanoyl-CoA = CoA + O-hexadecanoyl-(R)-carnitine (R)-carnitine + octanoyl-CoA = CoA + O-octanoyl-(R)-carnitine (R)-carnitine + decanoyl-CoA = CoA + O-decanoyl-(R)-carnitine (R)-carnitine + dodecanoyl-CoA = CoA + O-dodecanoyl-R-carnitine (R)-carnitine + tetradecanoyl-CoA = CoA + O-tetradecanoyl-(R)-carnitine (R)-carnitine + octadecanoyl-CoA = CoA + O-octadecanoyl-(R)-carnitine (R)-carnitine + eicosanoyl-CoA = CoA + O-eicosanoyl-(R)-carnitine (9Z)-tetradecenoyl-CoA + (R)-carnitine = CoA + O-(9Z)-tetradecenoyl-(R)-carnitine (5Z)-tetradecenoyl-CoA + (R)-carnitine = CoA + O-(5Z)-tetradecenoyl-(R)-carnitine (9Z)-octadecenoyl-CoA + (R)-carnitine = CoA + O-(9Z)-octadecenoyl-(R)-carnitine (R)-carnitine + 4,8-dimethylnonanoyl-CoA = CoA + O-4,8-dimethylnonanoyl-(R)-carnitine Lipid metabolism; fatty acid beta-oxidation. Belongs to the carnitine/choline acetyltransferase family.