Extreme Catalytic Power of Ketosteroid Isomerase Related to the Reversal of Proton Dislocations in Hydrogen-Bond Network.

Dynamic electrostatic catalytic field (DECF) vectors derived from transition state and reactant wavefunctions for the two-step reaction occurring within ketosteroid isomerase (KSI) have been calculated using MP2/aug-cc-pVTZ and lower theory levels to determine the magnitude of the catalytic effect and the optimal directions of proton transfers in the KSI hydrogen-bond network. The most surprising and meaningful finding is that the KSI catalytic activity is enhanced by proton dislocations proceeding in opposite directions for each of the two consecutive reaction steps in the same hydrogen network. Such a mechanism allows an ultrafast switching of the catalytic proton wire environment, possibly related to the exceptionally high KSI catalytic power.