The binding of NAD(+) and NADH to glycerol 3-phosphate dehydrogenase was studied in the pH range 6.0-9.0 at 25 degrees C and in the temperature range 16-43 degrees C at pH7.0. 2. The second-order velocity constants for the combination of NADH with the enzyme in the pH range 6.0-9.0 and for the combination of NAD(+) with the enzyme at pH6.0 were determined. 3. The velocity constant for the dissociation of the enzyme-NAD(+) complex at pH6.0 was measured.