Binding of reduced and oxidized nicotinamide adenine dinucleotide to pig heart supernatant malate dehydrogenase.
The association reactions of NADH and NAD+ with dimeric pig heart supernatant malate dehydrogenase (s-MDH) have been measured at pH 6 and 8 by calorimetric and fluorescence methods, and the thermodynamic parameters describing these reactions have been evaluated. Coenzyme binding is associated with the uptake of 0.55 mol of H+/mol of NADH at pH 8 and 0.19 mol of H+ at pH 6. No significant effect of NAD+ binding on proton binding was observed. Increase in ionic strength strongly affects the free energies of binding of NAD+ and NADH. No cooperativity was observed in the enthalpy or free energy changes for binding of NAD+ or NADH. The differences in free energy of binding of NAD+ and NADH and the effect of pH on binding of NADH are entropy based. These effects are interpreted as reflecting a small number of interactions within the active site that are predominantly ionic.
D000818:Animals; D003600:Cytosol / Q000201:enzymology; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology*; D009243:NAD; D010084:Oxidation-Reduction; D011485:Protein Binding; D013552:Swine; D013816:Thermodynamics
D009243:NAD; D008291:Malate Dehydrogenase