The reaction of ornithine aminotransferase with ornithine

Rat liver ornithine aminotransferase is found to exchange the pro-S hydrogen on the delta-carbon atom of ornithine exclusively, thus showing that the mammalian enzyme transfers the delta-amino group and not the alpha-amino group as has been demonstrated with the plant enzyme [Mestichelli, Gupta & Spenser (1979) J. Biol. Chem. 254, 640-647]. The enzyme also transfers the alpha-amino group of glutamate and the kinetics of the half reactions between the enzyme and both amino acids are compared. Rate and dissociation constants for both reactions are determined.