Carnitine-acylcarnitine translocase

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solute carrier family 25 (carnitine/acylcarnitine translocase), member 20
Symbol SLC25A20
Alt. symbols CACT
Entrez 788
HUGO 1421
OMIM 212138
RefSeq NM_000387
UniProt O43772
Other data
Locus Chr. 3 p21.31

Carnitine-acylcarnitine translocase is responsible for transporting both carnitine-fatty acid complexes and carnitine across the inner mitochondrial membrane.


This enzyme is required since fatty acids cannot cross the mitochondrial membranes without assistance. The fatty acid is firstly bound to CoA and may cross the external mitochondrial membrane. It then exchanges the CoA for carnitine by the action of the enzyme carnitine palmitoyltransferase I. The complex then enters the mitochondrial matrix thanks to facilitated diffusion by carnitine-acylcarnitine translocase. Here, the acyl-cartinine complex is disrupted by carnitine palmitoyltransferase II and the fatty acid rebinds to CoA. Carnitine then diffuses back across the membrane by carnitine-acylcarnitine translocase into the mitochondrial intermembrane space. This is called the carnitine shuttle system.

Clinical significance[edit]

A disorder is associated with carnitine-acylcarnitine translocase deficiency. This disorder prevents the shuttle-like action of carnitine from assisting fatty acids across the mitochondrial membrane and therefore there is decreased fatty acid catabolism. The result of this is an increased number of fat droplets within muscles and liver, decreased tolerance to long term exercise, inability to fast for more than a few hours, muscle weakness and wasting, and a strong acidic smell on the breath (due to protein breakdown).

Acyl-CoA from cytosol to the mitochondrial matrix

Model organisms[edit]

Model organisms have been used in the study of SLC25A20 function. A conditional knockout mouse line called Slc25a20tm1a(EUCOMM)Wtsi was generated at the Wellcome Trust Sanger Institute.[1] Male and female animals underwent a standardized phenotypic screen[2] to determine the effects of deletion.[3][4][5][6] Additional screens performed: - In-depth immunological phenotyping[7]


  1. ^ Gerdin AK (2010). "The Sanger Mouse Genetics Programme: high throughput characterisation of knockout mice". Acta Opthalmologica 88: 925-7.doi:10.1111/j.1755-3768.2010.4142.x: Wiley. 
  2. ^ a b "International Mouse Phenotyping Consortium". 
  3. ^ Skarnes WC, Rosen B, West AP, Koutsourakis M, Bushell W, Iyer V, Mujica AO, Thomas M, Harrow J, Cox T, Jackson D, Severin J, Biggs P, Fu J, Nefedov M, de Jong PJ, Stewart AF, Bradley A (Jun 2011). "A conditional knockout resource for the genome-wide study of mouse gene function". Nature 474 (7351): 337â€"42. doi:10.1038/nature10163. PMC 3572410. PMID 21677750. 
  4. ^ Dolgin E (Jun 2011). "Mouse library set to be knockout". Nature 474 (7351): 262–3. doi:10.1038/474262a. PMID 21677718. 
  5. ^ Collins FS, Rossant J, Wurst W (Jan 2007). "A mouse for all reasons". Cell 128 (1): 9â€"13. doi:10.1016/j.cell.2006.12.018. PMID 17218247. 
  6. ^ White JK, Gerdin AK, Karp NA, Ryder E, Buljan M, Bussell JN, Salisbury J, Clare S, Ingham NJ, Podrini C, Houghton R, Estabel J, Bottomley JR, Melvin DG, Sunter D, Adams NC, Sanger Institute Mouse Genetics Project, Tannahill D, Logan DW, Macarthur DG, Flint J, Mahajan VB, Tsang SH, Smyth I, Watt FM, Skarnes WC, Dougan G, Adams DJ, Ramirez-Solis R, Bradley A, Steel KP (2013). "Genome-wide generation and systematic phenotyping of knockout mice reveals new roles for many genes". Cell 154 (2): 452–64. doi:10.1016/j.cell.2013.06.022. PMID 23870131. 
  7. ^ a b "Infection and Immunity Immunophenotyping (3i) Consortium".