Enzyme electrodes lysine

Enzyme electrodes for the amino acids tyrosine and lysine have been... 

Chemically binding enzymes to nylon net is very simple and gives strong mechanically resistant membranes (135). The nylon net is first activated by methylation and then quickly treated with lysine. Finally, the enzyme is chemically bound with GA. The immobilized disks are fixed direcdy to the sensor surface or stored in a phosphate buffer. GOD, ascorbate oxidase, cholesterol oxidase, galactose oxidase, urease, alcohol oxidase (135), and lactate oxidase (142) have been immobilized by this procedure and the respective enzyme electrode performance has been established. 

Recently, selective oxidases for L-lysine (EC 1.4.3.-) (Romette et al., 1983) and L-glutamate (EC 1.4.3.11) have been employed in enzyme electrodes. Wollenberger et al. (1989) developed a sensor based on glutamate oxidase from Streptomyces endus, which permits selective measurement of glutamic acid between 1 pmol/1 and 1 mmol/1 with a sample frequency of 120/h. In contrast, a sensor using an analogous... 

Between 15 and 20 analyzers based on enzyme electrodes are on the market worldwide. They are one-parameter instruments for the measurement of glucose, galactose, uric add, choline, ethanol, lysine, lactate, pesti-ddes, sucrose, lactose, and the activity of a-amylase (Table 23). They provide for a negligible enzyme consumption of less than 1 pg per sample. 

Figure 3. Two-stepmodiiication of a PT-based enzyme electrode, (a) Electrochemical formation of the functionalized activated ester FT. (b) Covalent binding of GOD via its lysine residues to the activated carboxy groups at the surface of the polymer (taken from [554]).

In another biosensor construction variant, an enzyme electrode based on tyrosinase immobilized with ordered mesoporous carbon-Au (OMC-Au), L-lysine membrane and Au nanoparticles (tyrosinase/OMC-Au/L-lysine/Au) was combined with ANNs for the simultaneous determination of catechol and hydroquinone in compost bioremediation of municipal solid waste [35]. Limits of detection achieved were below 1 pM, demonstrating this is an appropriate tool for the quantitative study of a composting system. 

White W.C. and Guilbault G.G. (1978) Lysine specific enzyme electrode for determination of lysine in grains and foodstuffs. Anal. Chem.,SQ, 1481-1486. 

Weissbach F., Kreibich G., Bartels K. and Schiilke W. (1988) Rapid determination of L-lysine with an enzyme electrode by steady-state and kinetic measurement. Acta Biotechnol., 8,269-274. 

Romette J.L., Yang J.S., Kasukabe H. and Thomas D. (1983) Enzyme electrode for specific determination of L-lysine. Biotech. Bioeng., 25, 2557-2566. 

Enzymes have been attached to a nylon matrix (135-13 7), a pig intestine (138), the hydrophobic membrane of a gas-selective sensor (139), and controlled pore glass (140). Recent comparative studies of the coupling agents GA and benzoquinone support the preferential use of benzoquinone for binding GOD to nylon mesh (13 7), or to cellulose acetate membranes (141) with lysine (13 7). Both investigations report robust electrode behaviors with respect to prolonged exposure to glucose, while lifetimes of the membrane electrodes were ca. 3 months. 

L-Amino acid enzymes immobilized on O2 electrodes are used to determine methionine, leucine, phenylalanine, tyrosine, cysteine, lysine, and isbleucine... 

Applications. A biotinylated GOX-based biosensor was developed based on a new electropolymerized material consisting of a pol3rp3uidyl complex of ruthenium(II) functionalized with a pyrrole group [90]. Because histidine, lysine and arginine functions also coordinate Os /Os , biosensors based on co-electrodeposited GOX, HRP, soybean peroxidase (SBP) and laccase with redox Os /Os polymer have been developed [89]. A metal chelate formed by nickel and nitrilotriacetic acid was used to modify a screen-printed electrode surface. The functionalized support allowed stable attachment of acetylcholinesterase and the resulting biosensor was used for sensitive detection of organophosphorus insecticides [91]. This method is attractive because it ensures a controlled and oriented enzyme immobilization, considerably improving the sensitivity and the detection limit. 

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