Ab initio calculations are used to test a recent suggestion that enzymic catalysis can be aidedby 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 veryshort, and the proton transfer profile contains a very low energy barrier. There is no special stabilization associated with the disappearance of the transferbarrier or equalization of the pKa’s.