FUNCTION AND ROLE OF NAD+ IN MECHANISM OF ACTION OF RABBIT-MUSCLE GLYCERALDEHYDEPHOSPHATE DEHYDROGENASE

1. 1. NAD+ is required for the oxidation of NADH by 1,3-diphosphoglycerate or acetyl phosphate. 2. 2. The maximal rate of acetyl phosphate reduction by NADH or APADH is reached when about 3 moles NAD+ per mole enzyme are added. Larger amounts of NAD+ inhibit with a Ki (NADH as substrate) equal to 45 μM. 3. 3. The NAD-binding site with the lowest affinity for NAD+ appears to be the most active in the dehydrogenase reaction. Under optimal conditions the E-(NAD)3 complex is the catalytically active enzyme. 4. 4. The E-(NAD)3 complex appears also to be the form with maximal catalytic activity in the transferase reactions. 5. 5. NAD+ can be replaced by APAD+ in both the dehydrogenase and arsenolysis reactions. © 1969.