Ornithine aminotransferase, mitochondrial (OAT)

Ornithine aminotransferase, mitochondrial (OAT) is a pyridoxal 5’-phosphate-dependent enzyme located in the mitochondrial matrix, encoded by the OAT gene on chromosome 10. OAT catalyzes the reversible transamination of the delta-amino group from L-ornithine to α-ketoglutarate, generating L-glutamate 5-semialdehyde and L-glutamate—a key step that links ornithine and proline metabolism, also affecting glutamate and GABA pools. OAT is predominantly expressed in the liver, kidney, brain, and retina. Mutations in OAT lead to the rare inherited disorder gyrate atrophy of the choroid and retina, characterized by progressive vision loss due to retinal degeneration. The enzyme functions as a homotetramer, with activity reliant on pyridoxal phosphate (vitamin B6) as a cofactor. No approved drug directly targets OAT, though vitamin B6 supplementation is sometimes used with limited success in patients with OAT deficiency.

Other names

Ornithine delta-aminotransferaseOrnithine--oxo-acid aminotransferaseOAT2.6.1.13

Not directly manipulated by currently approved drugs; in deficiency states, some attempt to stabilize folding/catalytic activity with vitamin B6 as it is a required cofactor, acting through coenzyme support rather than classical inhibition/activation.