Partial purification and properties of alanine and aspartate aminotransferases in the midgut tissue of the silkworm, Bombyx mori (Lepidoptera: Bombycidae)

Alanine aminotransferase (E.C. 2.6.1.2.) and aspartate aminotransferase (E.C. 2.6.1.1.) extracted from the midgut of the silkworm were partially purified approximately 120-fold. The molecular weights of alanine AT-ase and aspartate AT-ase were 69, 000 and 68, 000, and the optimum pH values were 7.6 and 7.0, respectively. The Km values of alanine At-ase for alanine and α-ketoglutarate were 6.2×10-3M and 2.3×10-4M, and the Km values of aspartate AT-ase for aspartate and α-ketoglutarate were 3.6×10-4M and 2.0×10-4M. Hydroxylamine inhibited alanine AT-ase activity and enzyme activity was recovered by pyridoxal-P. Alanine AT-ase inhibited by p-CMB was reactivated by the addtion of DTT.