Citrin is one of two isoforms of these mitochondrial calcium-activated glutamate/aspartate carriers found in humans and is predominately expressed in non-excitable tissues.

Upon entering the mitochondrial matrix, malate is converted back into oxaloacetate to participate in the citric acid cycle.

Upon the unbinding of calcium, the first and second EF motifs within the N-terminal domain block off and close the opening, preventing the passage of substrates.

[5] Type II citrullinemia is a liver disease caused by mutations in the SLC25A13 gene, which codes for the citrin protein.

Most of these mutations lead to an unfunctional citrin protein, meaning it cannot work to properly transport aspartate from the mitochondria to the cytosol.