Bioelectrocatalysis, mediatorless

A.L. Ghindilis, T.G. Morzunova, A.V. Barmin and I.N. Kurochkin, Potentiometric biosensors for cholinesterase inhibitor analysis based on mediatorless bioelectrocatalysis, Biosens. Bioelectron, 11 (1996) 873-880. 

The structure and physicochemical properties of the enzymes which have been used to date to promote electrochemical reactions are briefly outlined. Methods of their immobilization are described. The status of research on redox transformations of proteins and enzymes at the electrode-electrolyte interface is discussed. Current concepts on the ways of conjugation of enzymatic and electrochemical reactions are summarized. Examples of bioelectrocatalysis in some electrochemical reactions are described. Electrocatalysis by enzymes under conditions of direct mediatorless transport of electrons between the electrode and the enzyme active center is considered in detail. Lastly, an analysis of the status of work pertaining to the field of sensors with enzymatic electrodes and to biofuel cells is provided. 

The observations listed above enable us to conclude that under the conditions of mediatorless bioelectrocatalysis, the adsorbed enzymes are functioning in a state close to the native one. Therefore, there is no basis for the assumption that the orbitals of the metal atom or of any other groups in the active center overlap with those of the electroconductive substrate. In the presence of such a direct overlap we would expect a significant change in the functioning mechanism of the active center. Moreover, the active center of the enzymes lies, as a rule, rather deep in the hydrophobic space of the protein globule. ... 

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