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- Heiskanen, Arto, et al.
(author)
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Amperometric monitoring of redox activity in living yeast cells: comparison of menadione and menadione sodium bisulfite as electron transfer mediators
- 2004
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In: Electrochemistry Communications. - : Elsevier BV. - 1388-2481. ; 6:2, s. 219-224
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Journal article (peer-reviewed)abstract
- An amperometric method was applied for real-time monitoring of intracellular redox enzyme activity. Baker’s yeast (Saccharomyces cerevisiae) cells were immobilized on platinum microband electrodes and mediated anodic currents were measured. The currents were observed in the absence and in the presence of glucose as a source of reducing equivalents, NADH and NADPH. 2-Methyl-1,4-naphthoquinone (menadione, vitamin K3) and water soluble 2-methyl-1,4-naphthoquinone sodium bisulfite (menadione sodium bisulfite MSB) were compared as artificial electron acceptors for their ability to transduce internal cellular redox activity into electrode current. It was found that hydrophobic menadione was superior to its water-soluble bisulfite derivative for probing whole intact cells.
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| 3. |
- Khampha, Wanida, et al.
(author)
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Specific detection of L-glutamate in food using flow-injection analysis and enzymatic recycling of substrate
- 2004
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In: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 518:1-2, s. 127-135
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Journal article (peer-reviewed)abstract
- A flow injection analysis (FIA) system for specific determination of L-glutamate in food samples based on a bi-enzymatic amplification system has been developed. The content of L-glutamate in the sample was amplified by cycling between L-glutamate dehydrogenase (GIDH) and a novel enzyme, D-phenylglycine aminotransferase (D-PhgAT). In this system, GIDH converts L-glutamate to 2-oxoglutarate with concomitant reduction of NAD(+) to NADH. D-PhgAT transfers an amino group from D-4-hydroxyphenylglycine to 2-oxoglutarate, thus recycling L-glutamate. Accumulation of NADH in the course of the enzymatic recycling was monitored both by fluorescence and UV absorbance and used for quantification of L-glutamate. The assay was characterized by high long-term stability (at least 70 days) and good reproducibility (within-day and between-day RSDs were 4.3-7.3% and 8.9%). The fluorimetric assay was slightly more sensitive with a L-glutamate detection limit of 0.4 muM and linear range of 2.5-50 muM. The assay was specific for L-glutamate, with recoveries between 95-103% in the presence of 17 different amino acids tested one by one. The method was applied to analysis of real food samples and results were correlated with a commercial Boehringer Mannheim assay kit. (C) 2004 Elsevier B.V. All rights reserved.
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