Conformational mobility of proteins and activation energy of enzymatic charge transfer reactions: an analysis in dielectric formalism.
In calculating the medium reorganization energy and the activation energy of charge transfer enzymatic reactions, an allowance is made for the enhanced conformational mobility of the protein external region. The two-layer model is proposed, the outer layer having a higher static dielectric constant. The calculations show that the higher mobility in the outer layer causes some quantitative rather than qualitative changes. The main result obtained earlier is confirmed: the reorganization energy for charge transfer reaction in protein globule is much lower than in water and for this reason the activation energy also decreases. The higher dielectric constant of the outer layer somewhat favours the introduction of charge into active site and hence favours the natural selection of proteins as enzymes. This effect cannot exclude the necessity of other factors stabilizing ionic forms inside the protein globule. Freezing of conformational mobility (say, at low temperatures) hinders the charge transfer process as a consequence of the difficulty in equalizing the initial and final energy levels.
D001665:Binding Sites; D004560:Electricity; D004563:Electrochemistry; D004789:Enzyme Activation; D005615:Freezing; D008433:Mathematics; D008954:Models, Biological; D011487:Protein Conformation; D013816:Thermodynamics