... To define in detail the molecular mechanism of NAD+-dependent formate dehydrogenase, the pH dependences of various kinetic and spectroscopic parameters have been studied: Vmax, Km (NAD+), Km (formate), inhibition constants for structural analogues of substrate (NO3-) and product (CNS-, CNO-, N3-), CD and fluorescence properties. The value of Vmax, rate-limiting hydride transfer, is nearly constant throughout the entire pH range of enzyme stability (6.0-11.2) but decreases below 6. ...