The Nonexistence of Specially Stabilized Hydrogen Bonds in Enzymes
Journal of the American Chemical Society
American Chemical Society
Ab initio calculations are used to test a recent suggestion that enzymic catalysis can be aided by strengthening of a hydrogen bond in a key intermediate, occurring when this bond is shortened and the pKa’s of the two groups are equalized. The requisite amount of energy is not available in electrically neutral H-bonds; no additional strengthening can be accomplished by shortening such a bond. Interaction energies where one subunit is charged, on the other hand, can be very high. These bonds are intrinsically very short, and the proton transfer profile contains a very low energy barrier. There is no special stabilization associated with the disappearance of the transfer barrier or equalization of the pKa’s.
The Nonexistence of Specially Stabilized Hydrogen Bonds in Enzymes S. Scheiner, T. Kar J. Am. Chem. Soc. 1995 117 (26), 6970-6975.