OAT, also known as mitochondrial enzyme ornithine aminotransferase, is a key enzyme in the pathway that converts arginine and ornithine into the major excitatory and inhibitory neurotransmitters glutamate and GABA. ( L-ornithine + a 2-oxo acid = L-glutamate 5-semialdehyde + an L-amino acid.) Mutations that result in a deficiency of this enzyme cause the autosomal recessive eye disease Gyrate Atrophy. Recombinant OAT protein was expressed in E.coli and purified by using conventional chromatography techniques.