Catalyzes the transfer of the acyl group of long-chain fatty acid-CoA conjugates onto carnitine, an essential step for the mitochondrial uptake of long-chain fatty acids and their subsequent beta-oxidation in the mitochondrion (PubMed:16169268, PubMed:17030509). Plays an important role in hepatic triglyceride metabolism (By similarity). (R)-carnitine + hexadecanoyl-CoA = CoA + O-hexadecanoyl-(R)-carnitine Inhibited by malonyl-CoA. Lipid metabolism; fatty acid beta-oxidation. Homohexamer and homotrimer (By similarity). Identified in a complex that contains at least CPT1A, ACSL1 and VDAC1 (By similarity). Also identified in complexes with ACSL1 and VDAC2 and VDAC3 (By similarity). A conformation change in the N-terminal region spanning the first 42 residues plays an important role in the regulation of enzyme activity by malonyl-CoA. Complete lethality during early embryogenesis. Heterozygous mice are prone to liver steatosis. Compared to wild-type, heterozygotes show minor differences in blood glucose levels and in serum free fatty acid levels after fasting. Belongs to the carnitine/choline acetyltransferase family.