Conducting enzyme membrane

S. Yabuki. H. Shinohara, and M. Aizawa, Electro-conductive enzyme membranes, J. Chem. Soc., Chem. Commun. 945 (1989). 

POTENTIAL CONTROLLED ENZYMATIC ACTIVITY OF CONDUCTING ENZYME MEMBRANE... 

Potential-Controlled Enzymatic Activity of Conducting Enzyme Membrane... 

Initial preparative work with oxynitrilases in neutral aqueous solution [517, 518] was hampered by the fact that under these reaction conditions the enzymatic addition has to compete with a spontaneous chemical reaction which limits enantioselectivity. Major improvements in optical purity of cyanohydrins were achieved by conducting the addition under acidic conditions to suppress the uncatalyzed side reaction [519], or by switching to a water immiscible organic solvent as the reaction medium [520], preferably diisopropyl ether. For the latter case, the enzymes are readily immobilized by physical adsorption onto cellulose. A continuous process has been developed for chiral cyanohydrin synthesis using an enzyme membrane reactor [61]. Acetone cyanhydrin can replace the highly toxic hydrocyanic acid as the cyanide source [521], Inexpensive defatted almond meal has been found to be a convenient substitute for the purified (R)-oxynitrilase without sacrificing enantioselectivity [522-524], Similarly, lyophilized and powered Sorghum bicolor shoots have been successfully tested as an alternative source for the purified (S)-oxynitrilase [525],... 

In recent years the electrochemistry of the enzyme membrane has been a subject of great interest due to its significance in both theories and practical applications to biosensors (i-5). Since the enzyme electrode was first proposed and prepared by Clark et al. (6) and Updike et al. (7), enzyme-based biosensors have become a widely interested research field. Research efforts have been directed toward improved designs of the electrode and the necessary membrane materials required for the proper operation of sensors. Different methods have been developed for immobilizing the enzyme on the electrode surface, such as covalent and adsorptive couplings (8-12) of the enzymes to the electrode surface, entrapment of the enzymes in the carbon paste mixture (13 etc. The entrapment of the enzyme into a conducting polymer has become an attractive method (14-22) because of the conducting nature of the polymer matrix and of the easy preparation procedure of the enzyme electrode. The entrapment of enzymes in the polypyrrole film provides a simple way of enzyme immobilization for the construction of a biosensor. It is known that the PPy-... 

There are four principal protein targets with which illicit dmgs can interact enzymes, membrane carriers, ion charmels, and receptors (Lambert, 2004). Receptors are macromolecules involved in chemical signaling between and within cells and activated receptors directly or indirectly regulate cellular biochemical processes (e.g., ion conductance, protein phosphorylation, DNA transcription, and enzymatic activity), which, in turn, can affect the homoeostasis of cells and organisms. 

Electrochemically synthesized polypyrrole-enzyme membranes have been shown to be enzymatically active and electrically conductive. Membrane-bound GOD is electrochemically regenerated from the reduced form of GOD. The enzyme activity of membrane-bound ADH can be electrochemically regulated. 

A platinum disk electrode was electrolytically platinized in a platinum chloride solution to increase the surface area and enhance the adsorption power. The platinized platinum electrode was then immersed in a solution containing 10 mg ml l ADH. 0.75 mM and 6.2 mM NAD. After sufficient adsorption of these molecules on the electrode surface, the electrode was transferred into a solution containing 0.1 M pyrrole and 1 M KC1. Electrochemical polymerization of pyrrole was conducted at +0.7 V vs. Ag/AgCl. The electrolysis was stopped at a total charge of 1 C cm 2. An enzyme-entrapped polypyrrole membrane was deposited on the electrode surface. 

This broad class of hydrolases constitutes a special category of enzymes which bind to and conduct their catalytic functions at the interface between the aqueous solution and the surface of membranes, vesicles, or emulsions. In order to explain the kinetics of lipolysis, one must determine the rates and affinities that govern enzyme adsorption to the interface of insoluble lipid structures -. One must also account for the special properties of the lipid surface as well as for the ability of enzymes to scooC along the lipid surface. See specific enzyme Micelle Interfacial Catalysis... 

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