  Previous kinetic models had assumed that the reaction medium was reacting at
random and without a turnover associated to thermodynamics exchanges, with a
rigid active site on the enzyme. The experimental studies show that coupling
factor 1 (CF1) from spinach chloroplasts has latent ATPase activity, which
become expressed after heat-treatment and incubation with calcium. The
sigmoidal kinetics observed on the competitive effect of glycerol on water
saturating a protein, suggests that the role of the hydration shell in the
catalytic mechanism of the CF1-ATPase, modify the number of water molecules
associated with the conformational turnover required for active site activity.
It is assume that the water associated to the hydrophilic state of the enzyme
produces a fit-in of the substrate to form (ES), follow by the catalytic action
with product formation (EP). This one induces the dissociation of water and
increases the hydrophobic attractions between R-groups. The latter, becomes the
form of the enzyme interacting with water to form the dissociated free enzyme
(E) and free product (P). Glycerol dependent suppression of the water dynamics
on two interacting sites configuration shows a change in the
H-bond-configuration. The thermodynamics modeling requires an energy
expenditure of about 4kcal/mol per each H-bond in turnover. Glycerol determined
a turnover of 14 molecules of water released from the active sites to reach the
inactive form of the enzyme. The entropy generated by turnover of the fit-in
and -out substrate and product from the protein could be dissipated-out of the
enzyme-water system itself. Coupling with the surrounding water clusters allows
to recreate H-bonds. This should involve a decrease in the number of H-bonds
present in the clusters. These changes in the mass action capability of the
water clusters could eventually become dissipated through a cooling effect.

Biomolecules