Is there bibliography about how amino acids side chains of a protein affect the reduction potential of NAD, so a specific enzyme catalyze better the oxidation of NADH or the reduction of NAD+? For instance, hydrophobic or electrostatic interactions at the nicotinic ring...or H-bonds and the carboxynamide group? I need to design site-directed variants so an enzyme that catalyze NAD+ reduction and substrate oxidation, can catalyze also the reverse reaction. I am assuming taht the reduction potential of NAD+ in solution would be different to that of the NAD+ bound to the enzyme. Is that correct? Thank you!