On the enzymatic activation of NADH.

Atomic (1 A) resolution x-ray structures of horse liver alcohol dehydrogenase in complex with NADH revealed the formation of an adduct in the active site between a metal-bound water and NADH. Furthermore, a pronounced distortion of the pyridine ring of NADH was observed. A series of quantum chemical calculations on the water-nicotinamide adduct showed that the puckering of the pyridine ring in the crystal structures can only be reproduced when the water is considered a hydroxide ion. These observations provide fundamental insight into the enzymatic activation of NADH for hydride transfer.