Protein and Identifier (UniProt ID for Human Protein) | Involvement | Localization | Reference |
---|---|---|---|
Carnitine acetyltransferase (CrAT) EC 2.3.1.7 (UniProtKB: P43155) | Catalyzes the reversible transfer of acyl groups (up to C4) from carnitine to CoA and regulates the acyl-CoA/CoA ratio and availability of free CoA during intensified fatty acid metabolism. | Mitochondrial matrix, peroxisomal matrix, endoplasmic reticulum, nucleus, and cardiomyocyte cytosol | Wu et al., 2003; Hsiao et al., 2004; Stephens et al., 2007 |
Carnitine octanoyltransferase (CrOT) EC 2.3.1.137 (UniProtKB: Q9UKG9) | Catalyzes reversible transfer of acyl groups (C6–12, can go up to C16) from CoA to carnitine. Metabolism of branched chain fatty acids. | Peroxisomal matrix | Ferdinandusse et al., 1999; Jogl et al., 2005 |
Carnitine palmitoyltransferase 1 (CPT1) EC 2.3.1.21 | Catalyzes reversible transfer of the acyl group of long-chain fatty acid-CoA conjugates onto carnitine. Broad specificity to acyl group, over the range of C8–C18, optimal substrate palmitoyl-CoA. Forward reaction inhibited by palmitoylcarnitine and malonyl-CoA. | Outer mitochondrial membrane | McGarry and Brown, 1997 |
CPT1A – liver isoform UniProtKB: P50416 | Expressed in most tissues. Low Km value for carnitine, sensitive to malony-CoA. | Outer mitochondrial membrane | |
CPT1B – muscle isoform UniProtKB: Q92523 | Highest expression in heart and skeletal muscle, no expression in liver and kidney. High Km value for carnitine, sensitive to malony-CoA. | Outer mitochondrial membrane | |
CPT1C – brain isoform UniProtKB: Q8TCG5 | Highest expression in brain and testis. Catalytic activity negligible but can bind malonyl-CoA. Regulates energy homeostasis and involved in ceramide biosynthesis and regulation. | Conflicting reports on localization in mitochondria or endoplasmic reticulum | Price et al., 2002; Wolfgang et al., 2006; Sierra et al., 2008 |
Carnitine palmitoyltransferase 2 (CPT2) EC 2.3.1.21 (UniProtKB: P23786) | Catalyzes the transfer of the acyl group of long-chain fatty acid- carnitine conjugates onto CoA. Loss of CPT2 disables the acylcarnitine-mediated mitochondrial oxidation of long-chain fatty acids. | Inner mitochondrial membrane | Pereyra et al., 2017 |
Carnitine/acylcarnitine translocase (CACT) (UniProtKB: O43772) | Transport of acylcarnitines and carnitine across the mitochondrial inner membrane to and from mitochondrial matrix. Support of mitochondrial fatty acid-oxidation pathway. | Inner mitochondrial membrane | Console et al., 2014 |
Organic cation transporter 1 (OCT1) SLC22A1 (UniProtKB: O15245) | Involved in hepatic acylcarnitine efflux. Associated with serum acylcarnitine levels. | Cell membrane | Kim et al., 2017 |
Organic cation novel type 2 transporter (OCTN2) SLC22A5 (UniProtKB: O76082) | Involved in transport of acetylcarnitine. | Cell membrane | Kido et al., 2001; Kobayashi et al., 2007 |