Carnitine-acylcarnitine translocase (CACT) is responsible for passive transport of carnitine and carnitine-fatty acid complexes and across the inner mitochondrial membrane as part of the carnitine shuttle system.

Quick Facts SLC25A20, Identifiers ...

SLC25A20
Identifiers
Aliases	SLC25A20, CAC, CACT, Carnitine-acylcarnitine translocase, solute carrier family 25 member 20
External IDs	OMIM: 613698 MGI: 1928738 HomoloGene: 331 GeneCards: SLC25A20
Gene location (Human) Chr. Chromosome 3 (human)[1] Band 3p21.31 Start 48,856,926 bp[1] End 48,898,904 bp[1]
Gene location (Mouse) Chr. Chromosome 9 (mouse)[2] Band 9|9 F2 Start 108,539,287 bp[2] End 108,561,840 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in right lobe of liver left ventricle gastrocnemius muscle duodenum jejunal mucosa monocyte left adrenal gland right adrenal gland right ventricle rectum Top expressed in brown adipose tissue interventricular septum intercostal muscle soleus muscle myocardium of ventricle thoracic diaphragm left lobe of liver right ventricle extraocular muscle digastric muscle More reference expression data BioGPS n/a
Gene ontology Molecular function acyl carnitine transmembrane transporter activity carnitine:acyl carnitine antiporter activity carnitine transmembrane transporter activity transmembrane transporter activity Cellular component membrane mitochondrion cytosol mitochondrial inner membrane integral component of membrane Biological process carnitine shuttle acyl carnitine transmembrane transport mitochondrial transport carnitine transport carnitine transmembrane transport transport Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 788 57279 Ensembl ENSG00000178537 ENSMUSG00000032602 UniProt O43772 Q9Z2Z6 RefSeq (mRNA) NM_000387 NM_020520 RefSeq (protein) NP_000378 NP_065266 Location (UCSC) Chr 3: 48.86 – 48.9 Mb Chr 9: 108.54 – 108.56 Mb PubMed search [3] [4]
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Fatty acyl–carnitine can diffuse from the cytosol across the porous outer mitochondrial membrane to the intermembrane space, but must utilize CACT to cross the nonporous inner mitochondrial membrane and reach the mitochondrial matrix. CACT is a cotransporter, returning one molecule of carnitine from the matrix to the intermembrane space as one molecule of fatty acyl–carnitine moves into the matrix.^[5]

A disorder is associated with carnitine-acylcarnitine translocase deficiency. This disorder disrupts the carnitine shuttle system from moving fatty acids across the mitochondrial membrane, leading to a decrease in fatty acid catabolism. The result is an accumulation of fatty acid 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 catabolism).