Dye-linked dehydrogenases catalyze the electron transfer from amino acids, amines and alcohols to artificial electron acceptors such as 2,6-dichloroindophenol and ferricyanide. Their structural and functional information, and applications have been so far limited because of their low stability. We have carried out screening of the enzymes in hyperthermophiles and found three kinds of novel dye-linked proline dehydrogenases in hyperthermophilic archaea; tetrameric dye-linked L-proline dehydrogenase (αβγδ-type) from Thermococcus profundus, the octameric L-proline dehydrogenase (α_4β_4-type) from Pyrococcus horikoshii and tetrameric D-proline dehydrogenase from Pyrobaculum islandicum. We succeeded in biochemical characterization of the three enzymes and the 3D-structural analysis of the octameric enzyme, suggesting the presence of a novel electron transfer system in this hyperthermophile. In addition, we have constructed an electrochemical biosensor for L-proline determination using the stable dye-linked L-proline dehydrogenase as the application of dye-linked dehydrogenase.

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Polyphenols and Atherosclerosis Recently, the polyphenols in plant foods have attracted interest because of their possible effects on cardiovascular health. This paper provides an overview of our research on the effects of cocoa polyphenols on oxidation of LDL and atherosclerosis. Ingestion of polyphenol-rich cocoa prolonged the lag time (an index of LDL oxidative susceptibility) and decreased plasma levels of oxidized LDL in humans and prevented the formation of atherosclerotic lesion in experimental animals. Catechins in cocoa show high bioavailability, and approximately 25-30% of ingested catechins are detected in urine. After oral supplementation, catechin metabolites such as glucuronides and/or sulfate-conjugated and/or methylated forms are present in the blood. The catechin metabolites (glucuronides) in rats and humans are completely different structurally, and their antioxidative activity is maintained for longer periods in rats than in humans. On the other hand, ingestion of cacao products increased the level of HDL in humans, and this up-regulation of HDL might be due to an antioxidative effect of cacao. Thus, cacao polyphenols may reduce cardiovascular disease risk.

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Vitamin C (C) consists of reduced form L-Ascorbic acid (AsA) and oxidized form L-Dehydroascorbic acid (DAsA). It has been a research subject in nutrition and food science field whether the C activity of DAsA will be 1 or 0.5 when C efficacy of AsA is 1. In this study, we provided low-C diet to ten healthy females for three days until the experimental day. After that we divided them into AsA group and DAsA group, and orally administered 1 mmol of AsA crystal (176mg) and DAsA crystal (174mg). We measured the amount of C in their urine. The 24-hour total amounts of C in urine during the C lacking period were 9mg in AsA group and 5mg in DAsA group. After ingestion of C the amounts were 47mg in AsA group and 35mg in DAsA group. No statistical difference was found between both groups. The urine sampling was undertaken every 2 hours for 8 hours after ingestion of C. The 0-2 hour amount of C in urine in DAsA group was larger than that in AsA group. But other timezones did not show statistical difference between both groups.

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