Mode of binding of pyridoxal 5'-phosphate in rat liver ornithine aminotransferase.

1. Pyridoxal 5'-phosphate and pyridoxamine 5'-phosphate were effective for the association of apo-form II of ornithine aminotransferase [EC 2.6.1.13]; whereas other B6 derivatives, such as pyridoxal, pyridoxamine, pyridoxine and pyridoxine 5'-phosphate, had no effect on form II of this apoenzyme. 2. The pyridoxal 5'-phosphate contents of the native enzyme, and reconstituted forms I and II were determined by two different methods to be 1.5 moles, 2.5 moles and 3.3 moles of pyridoxal 5'-phosphate/mole of enzyme, respectively.