L-Malate-sensing electrode based on malate dehydrogenase and NADH oxidase |
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Authors: | Fumio Mizutani Soichi Yabuki Michihiko Asai |
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Institution: | Research Institute for Polymers and Textiles, 1-1-4 Higashi, Tsukuba, Ibaraki 305 Japan |
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Abstract: | An L-malate-sensing electrode was constructed from an oxygen electrode and a layer containing immobilized malate dehydrogenase (MDH) and NADH oxidase. MDH catalyses the dehydrogenation of L-malate by NAD+ and NADH oxidase catalyses the regeneration of NAD+ with the use of oxygen. The regeneration enables the L-malate oxidation to proceed efficiently even in a medium of neutral pH. At pH 8.0, L-malate in the concentration range 5 μM–1.5 mM can be measured. The relative standard deviation for the measurement is 1.2% (L-malate concentration, 0.2 mM; n=10). The present L-malate-sensing electrode is stable for 8 weeks. A two-electrode sensor system consisting of the L-malate-sensing electrode and an L-lactate-sensing electrode based on lactate oxidase was prepared and applied to the simultaneous determination of the two components in wines. |
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Keywords: | Amperometry Enzyme electrodes Lactate Malate Wines |
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