Biomedical subjects

Hiroyuki Nagaoka

Publications and source records attributed to Hiroyuki Nagaoka.

3 recordsLinked to original sources

PubMedDate not supplied

Chiral resolution function with immobilized food proteins.

We confirmed that an NAD(P)+-dependent secondary alcohol dehydrogenase (NAD(P)-E) can be easily and effectively isolated from pea, soybean, and wheat proteins immobilized with calcium alginate gel (IPP, ISP, and IWP, respectively). The estimated molecular mass of NAD(P)-E is 138.7 kDa, and the concentrations of NAD(P)-E in solution are 36.2 (IPP), 53.9 (ISP), and 93.7 (IWP) microg/mL. The NAD(P)-E oxidizes only (R)-isomers highly enantioselectively; thus, greater than 99% ee(s) of (S)-isomers can be obtained from corresponding rac-aryl methyl carbinols (1, 2a-6a, and 2b-7b). The amount of food protein needed for 1 g of substrate (B/S ratio) is approximately 20. Thus, in comparison to current biocatalysts, certain food proteins can serve as asymmetric reagent bases, providing easily obtained, low-cost natural catalysts with stereoselectivity, regioselectivity, and substrate specificity that work under mild conditions for asymmetric synthesis of organic compounds. Moreover, this "fourth" function of food may help build a sustainable society by synthesizing optically active secondary alcohols in an environmentally friendly manner.

Alcohols↗

PubMedDate not supplied

Ability of different biomaterials to enantioselectively catalyze oxidation and reduction reactions.

We studied the ability of different biomaterials to enantioselectively catalyze oxidation or reduction reactions with the help of substrate rac-1-m or p-ArCH(OH)Me and the 1-o-ArC(O)Me derivatives. Apoenzyme (NAD(P)(+)-dependent secondary alcohol dehydrogenase(NAD(P)-E)) and cofactor (NAD(P)(+)) were activated by preincubating immobilized aqueous plant leaf (e.g., young wheat leaves), cereal tissue (wheat bran), vegetable (e.g., carrot), and seaweed (e.g., wakame seaweed) solutions, and the NAD(P)-E oxidized only (R)-isomers highly enantioselectively. Thus, greater than 99% ee(s) of (S)-isomers (1m-5m and 1p-5p) can be obtained from corresponding rac-1-m or p-ArCH(OH)Me. Further, immobilized chlorella cells and immobilized baker's yeast can reduce highly stereoselectively; greater than 99% ee(s) of (S)-isomers (1o-5o) can be obtained from corresponding 1-o-ArC(O)Me. Specific use of each isomer ((S)-6 and (R)-6) with greater than 99% ee(s) of racemic-1-2-NpCH(OH)Me becomes possible through selective use of NAD(P)-E eluted from artemisia vulgaris indica leaves and young wheat leaves. We suggest that the pH of the reaction media can determine not only the direction of NAD(P)-E, toward enantioselectively catalyzed oxidation (pH > 7.0) or reduction reaction (pH < 7.0), but also the regioselective reactivity of NAD(P)-E to the substrate o- (pH < 7.0), m-, and p-substituted groups (pH > 7.0). Thus, in comparison to current biocatalysts, several biomaterials can serve as asymmetric reagent bases, providing easily obtained, low-cost natural catalysts with stereoselectivity, regioselectivity, and substrate specificity that work under mild conditions for asymmetric synthesis of organic compounds.

Alcohols↗

PubMedDate not supplied

Treatment of germinated wheat to increase levels of GABA and IP6 catalyzed by endogenous enzymes.

We found that the levels of bioactive products from wheat can be increased dramatically by manipulating germination conditions and taking advantage of the activity of endogenous enzymes. The yield of phytic acid (IP(6)) from wheat germinated in the presence of high, controlled levels of dissolved oxygen (188 +/- 28 mg/100 g wheat) was almost three times greater than that from wheat germinated with no supplemental oxygen (74 +/- 10 mg/100 g wheat). The yield of gamma-aminobutyric acid (GABA) from wheat germinated in the presence of uncontrolled levels of dissolved oxygen was 18 +/- 3 times greater than that from nonsupplemented wheat (1 mg/100 g wheat). The concentration of GABA was much greater in wheat germ than in whole wheat, and the yield of GABA from wheat germ processed with supplemental water (163 +/- 7 mg/100 g wheat germ) was notably greater than that from wheat germ processed with no supplemental water (100 +/- 2 mg/100 g wheat germ). In contrast, IP(6) was more concentrated in wheat bran, and the yield of IP(6) from wheat bran processed with supplemental water (3100 +/- 12 mg/100 g wheat bran) was notably higher than that from wheat bran processed with no supplemental water (2420 +/- 13 mg/100 g wheat bran). We conclude that the large amount of GABA extracted from wheat germ is likely due to high glutamate decarboxylase activity and low aminotransferase activity and that the large amount of IP(6) extracted from wheat bran is likely due to high levels of tyrosinase activity. Our findings indicate that bioactive molecules such as GABA and IP(6) can be successfully mass-produced by taking advantage of endogenous enzymatic activities.

Catalysis↗