On the role of Glu‐68 in alcohol dehydrogenase

Theoretical computations (molecular dynamics and combined quantum chemical and molecular mechanical geometry optimizations) have been performed on horse liver alcohol dehydrogenase. The results provide evidence that Glu‐68, a highly conserved residue located 0.47 nm from the catalytic zinc ion, may intermittently coordinate to the zinc ion. Structures with Glu‐68 coordinated to the zinc ion are almost as stable as structures with Glu‐68 at the crystal position and the barrier between the two configurations of Glu‐68 is so low that it can readily be bypassed at room temperature. There is a cavity behind the zinc ion that seems to be tailored to allow such coordination of Glu‐68 to the zinc ion. It is suggested that Glu‐68 may facilitate the exchange of ligands in the substrate site by coordinating to the zinc ion when the old ligand dissociates.