Kinetic studies of immobilized alpha-chymotrypsin in apolar solvents

The mechanism of alpha-chymotrypsin action has been probed by extending studies of native chymotrypsin to immobilized chymotrypsin, where the organic content of the solution can be raised to much higher levels and thus one can explicitly look at the role of water. When one does this, one finds that water only appears in the deacylation reaction. The premise that one can go from native chymotrypsin (souble) to immobilized chymotrypsin (insoluble) has been tested by several criteria. It has been found in many instances that the two are identical: in absolute rate, in pKa. They are, however, not identical to one another in binding, due to differences in diffusion, which is to be expected. Thus, mechanistically immobilized and native chymotrypsin are identical to one another and the use of immobilized chymotrypsin can be used to specify the mechanism even more: it must proceed through two tetrahedral intermediates and two acyl-enzyme intermediates.