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Enzyme electrodes pyruvate

LDH enzyme electrodes follow electrochemically NADH consumption or NAD" " formation (211). Electrochemically activated microcarbon electrodes can be utilized in conjunction with immobilized LDH to determine pyruvate in small volumes (50 pL) of cerebrospinal fluid within the concentration range 10 pM to 2 mM (234). The construction of pymvate oxidase electrodes operating either at positive potentials (H2O2 detection) or at negative potentials (oxygen depletion) (92) is described by... [Pg.95]

The different cosubstrate specificities of the lactate-oxidizing enzymes offer the use of a great variety of electrochemical indicator reactions in membrane sensors. In enzyme electrodes based on LDH the biochemical reaction has been coupled to the electrode via NADH oxidation, either directly or by using mediators or additional enzymes (see Section 3.2.1). This leads to a shift of the unfavorable reaction equilibrium by partial trapping of the reduced cofactor. Such a shift has also been achieved by using pyruvate oxidase coimmobilized with LDH (Mizutani, 1982). [Pg.127]

The concentrations of a number of analytically relevant compounds, such as creatinine, pyruvate, hormones, and drugs, are often so low that their assay with enzyme electrodes requires large sample volumes or is totally impossible. The detection limit of usual enzyme electrodes is... [Pg.220]

Fig. 137. Scheme of an on-line bedside analyzer for parallel determination of glucose, lactate, and pyruvate using enzyme electrodes. (Redrawn from Mascini, 1987). [Pg.315]

T. Yao, T. Yano, On-line microdialysis assay of L-lactate and pyruvate in vitro and in vivo by a flow-injection system with a dual enzyme electrode, Talanta 63 (2004) 771. [Pg.42]

Figure 17.6 (a) The principle of an accumulation biosensor, (b) Current-time curves for a sensor operated without and with intermediate accumulation. The difference in the steady state and peak currents represents the amplification of the sensor response, (c) Glycerol measurement without and with NADH accumulation on an enzyme electrode containing immobilized glycerol dehydrogenase, lactate dehydrogenase, and lactate monooxygenase. NADH is stripped by pyruvate addition after 6 min accumulation (reproduced with the permission of Elsevier Science Publishers BV). [Pg.447]

Figure I4-2 Schematic view of an enzyme electrode using a double recycling system for the determination of ATP or ADP. PK = pyruvate kinase HK = herokinase LOD = lactate oxidase LDH = lactate dehydrogenase PEP = phosphoenolpyruvat Reproduced from [327] with permission from Marcel Dekket, Inc. Figure I4-2 Schematic view of an enzyme electrode using a double recycling system for the determination of ATP or ADP. PK = pyruvate kinase HK = herokinase LOD = lactate oxidase LDH = lactate dehydrogenase PEP = phosphoenolpyruvat Reproduced from [327] with permission from Marcel Dekket, Inc.
Pyruvic acid Enzyme electrode Fixed pyruvic acid oxidase Diagnosis Oxygen electrode... [Pg.1134]

An important parameter in a number of fields is the study of inorganic phosphate. Recently, Kwan et al. [206,207] have reported on a screen-printed phosphate biosensor based on immobilised pyruvate oxidase (PyOD) for monitoring phosphate concentrations in a sequencing batch reactor system [206] and in human saliva [207]. The enzyme was immobilised by drop-coating a Nation solution onto the working electrode surface this was then covered by a poly(carbamoyl) sulfonate (PCS) hydrogel membrane. [Pg.539]

Construction principles and the mechanism for biosensors derived from enzymes. Combined enzymatic and electrochemical reactions proceeding on electrodes from various materials in electrolyte solutions promote development of many biosensor types for detection of glucose, amino acids, lactose, urea, pyruvate and other metabolites. Biosensors are successfully applied to environmental contamination control, medical diagnostics and the food industry. [Pg.289]

An interesting application for the oxidation of organic compounds is of electrochemical nature. Octacyano complexes have been used to monitor redox enzymes such as lactate oxidase (from Pediococcus sp.) and sarcosine oxidase (from Arthrobactersp.) in a suitable electrochemical system (114). Two equivalents of [M(CN)g] can, for example, be oxidized at the electrode surface to [M(CN)g], which in turn can oxidize the flavoproteien to its oxidized form. This in turn reacts with, for example, L-lactic acid to produce pyruvic acid. [Pg.280]

Sensors have also been constructed from some oxidases directly contacted to electrodes to give bioelectrocatalytic systems. These enzymes utilize molecular oxygen as the electron acceptor for the oxidation of their substrates. Enzymes such as catechol oxidase, amino acid oxidase, glucose oxidase, lactate oxidase, pyruvate oxidase, alcohol oxidase, xanthine oxidase and cholesterol oxidase catalyze the oxidation of their respective substrates with the concomitant reduction of O2 to H2O2 ... [Pg.2504]

The electrochemical detection utilized the re-oxidation of hexacyano-ferrate(II) on a platinum electrode. For pyruvate determination this assay was extended to a 3-enzyme system by the addition of glutamate p5u-uvate transaminase, which produces alanine from pyruvate. All enz5unes were used in solution in a reaction chamber of approximately 2 pi directly in front of the electrode. The cofactor NAD" " was coupled to dextran with a molecular weight of 40,000 to avoid its replacement for each assay. As the sensor responded to L-alanine and pyruvate again a differential measurement was required when a sample contained both compounds. It was applied to off-line monitoring of a cultivation of S. cerevisiae and data showed good correlation to the photometric assays. [Pg.200]

Gorton et al. reported carbon paste electrodes based on Toluidine Blue O (TBO)-methacrylate co-polymers or ethylenediamine polymer derivative and NAD" " with yeast alcohol dehydrogenase for the analysis of ethanol [152,153] and with D-lactate dehydrogenase for the analysis of D-lactic acid [154]. Use of electrodes prepared with dye-modified polymeric electron transfer systems and NAD+/NADH to detect vitamin K and pyruvic acid has also been reported by Okamoto et al. [153]. Although these sensors showed acceptable performances, insensitivity to ambient oxygen concentration, sensor stability and lifetime still need to be improved to obtain optimal dehydrogenase based enzyme biosensors. [Pg.364]

Fry has used a similar system for the enzymatic reduction of pyruvate to L-lactate. In this case, the one-electron transfer redox catalyst, methyl viologen, and the lipoamide dehydrogenase are coimmobilized within a Nafion cation-exchange layer on the surface of a reticulated vitreous carbon electrode. As production enzyme, L-lactate dehydrogenase (LDH) was employed [48], which was later stabilized considerably in the form of cross-... [Pg.1111]


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See also in sourсe #XX -- [ Pg.93 , Pg.95 ]




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