Carnitine-acylcarnitine translocase

solute carrier family 25 (carnitine/acylcarnitine translocase), member 20
Identifiers
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.

Function

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 via 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

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

Model organisms have been used in the study of SLC25A20 function. A conditional knockout mouse line called Slc25a20^{tm1a(EUCOMM)Wtsi} was generated at the Wellcome Trust Sanger Institute. Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion. Additional screens performed: - In-depth immunological phenotyping

Slc25a20 knockout mouse phenotype

Characteristic	Phenotype
All data available at.
Peripheral blood leukocytes 6 Weeks	Normal
Insulin	Normal
Haematology 6 Weeks	Normal
Homozygous viability at P14	Abnormal
Recessive lethal study	Normal
Body weight	Normal
Neurological assessment	Normal
Grip strength	Normal
Dysmorphology	Normal
Indirect calorimetry	Abnormal
Glucose tolerance test	Normal
Auditory brainstem response	Normal
DEXA	Normal
Radiography	Normal
Eye morphology	Normal
Clinical chemistry	Normal
Haematology 16 Weeks	Normal
Peripheral blood leukocytes 16 Weeks	Normal
Heart weight	Normal
Salmonella infection	Normal
Cytotoxic T Cell Function	Normal
Spleen Immunophenotyping	Normal
Mesenteric Lymph Node Immunophenotyping	Normal
Bone Marrow Immunophenotyping	Normal
Epidermal Immune Composition	Normal
Influenza Challenge	Normal