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Haraguchi K.,Japan National Food Research Institute
Carbohydrate Polymers | Year: 2010

An inulin fructotransferase (DFA III-producing) [EC] from Arthrobacter ureafaciens D13-3 was purified and characterized. The enzyme was purified from culture supernatant of the microorganism 22.3-fold with a yield of 23.6%. The enzyme showed maximum activity at pH 5.5 and 50 °C. The enzyme activity was stable up to 70 °C after 30 min heat treatment. The molecular mass of the enzyme was estimated to be 40 kDa by SDS-PAGE and 43 kDa by gel filtration, and the enzyme was considered to be a monomer. The smallest fructo-oligosaccharide as the substrate was estimated to be GF3 (nystose). The N-terminal amino acid sequence (12 amino acid residues) was analyzed as TTVYDTTVDVP. © 2010 Elsevier Ltd. All rights reserved.

Haraguchi K.,Japan National Food Research Institute
Carbohydrate Polymers | Year: 2013

A gene of inulin fructotransferase (DFA III-producing) [EC] from Arthrobacter sp. L68-1 was cloned and the nucleotide was sequenced. The gene encoded a signal peptide (32 amino acid residues) for a secretion, and the mature enzyme protein was estimated to be consisted with 410 amino acid residues. The molecular mass of the native enzyme was calculated as 43.7 kDa by the sequence data. The deduced amino acid sequence of the enzyme had 79.0% homology with that of the Arthrobacter globiformis C11-1, and had 77.4% homology with that of the Arthrobacter sp. H65-7. It also had 43.7% homology with that of inulin fructotransferase (DFA I-producing) [EC] from A. globiformis S14-3. The cloned enzyme was immobilized using Chitopearl BCW 3510 as a carrier. The immobilized enzyme was able to use 10 times without a significant loss of the enzyme activity. © 2012 Elsevier Ltd.

Ide T.,Japan National Food Research Institute | Ide T.,Jumonji University
British Journal of Nutrition | Year: 2014

In the present study, the mRNA levels of hepatic proteins involved in the drug metabolism of rats fed α-lipoic acid were evaluated by DNA microarray and real-time PCR analyses. Experimental diets containing 0, 0·1, 0·25 and 0·5 % (w/w) α-lipoic acid were fed to four groups of rats consisting of seven animals each for 21 d. DNA microarray analysis revealed that the diet containing 0·5 % α-lipoic acid significantly (P< 0·05) increased the mRNA levels of various phase I drug-metabolising enzymes up to 15-fold and phase II enzymes up to 52-fold in an isoenzyme-specific manner. α-Lipoic acid also up-regulated the mRNA levels of some members of the ATP-binding cassette transporter superfamily, presumed to be involved in the exportation of xenobiotics, up to 6·6-fold. In addition, we observed that α-lipoic acid increased the mRNA levels of many proteins involved in antioxidation, such as members of the thiol redox system (up to 5·5-fold), metallothioneins (up to 12-fold) and haeme oxygenase 1 (1·5-fold). These results were confirmed using real-time PCR analysis, and α-lipoic acid dose dependently increased the mRNA levels of various proteins involved in drug metabolism and antioxidation. Consistent with these observations, α-lipoic acid dose dependently increased the hepatic concentration of glutathione and the activities of glutathione reductase and glutathione transferase measured using 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene as substrates, but decreased the hepatic and serum concentrations of malondialdehyde. In conclusion, the present study unequivocally demonstrated that α-lipoic acid increases the mRNA expression of proteins involved in drug metabolism and antioxidation in the liver. Copyright © The Author 2014.

Nei D.,Japan National Food Research Institute
Food Control | Year: 2014

Histamine is one cause of scombroid foodborne poisoning. The bacterial decarboxylation of amino acids leads to the formation of biogenic amines such as histamine. This study examined histamine accumulation in tuna and yellowtail fillets that had been sterilized by gamma irradiation to confirm whether factors other than bacterial activity are able to induce histamine accumulation. Fish fillets were sterilized by gamma irradiation at 35kGy and stored for 7 days at 5, 15, or 25°C, and the resulting histamine concentrations were measured. The histamine concentrations in all tested samples of tuna and yellowtail were below the detection limit of the assay used (<10mg/kg). In contrast, the tuna and yellowtail meats inoculated with Morganella morganii, a known histamine-producing bacterium, showed significant histamine accumulation at 15 and 25°C. These results indicated that non-bacterial factors do not promote histamine accumulation. Therefore, the proper control of histamine-producing bacteria is both necessary and sufficient to prevent histamine accumulation. © 2013 Elsevier Ltd.

Tsuzuki W.,Japan National Food Research Institute
Food Chemistry | Year: 2011

To elucidate the relation between heat-induced cis/trans isomerisation and thermal oxidative degradation of double bonds in unsaturated lipids, we investigated the effects of several edible antioxidants on these two molecular structural changes of double bonds in triolein (cis-9, 18:1) and trilinolein (cis-9, cis-12, 18:2), which were heated at 180°C. trans Isomerisation and oxidative degradation of each cis double bond in the triacylglycerols during heating were evaluated on the basis of the increase in the amount of trans isomers and decrease in the amount of cis isomers by gas chromatography analysis. The synchronous suppression in trans isomerisation and cis deterioration of double bonds in these triacylglycerols were found by addition of antioxidants, whose inhibitory effects were associated with their kinds and concentrations. When triolein was heated in the presence of antioxidant, suppression of heat-induced trans isomerisation was directly proportional to that of cis deterioration. The results of our analysis suggested that the appropriate addition of antioxidants to edible oils during processing and cooking would facilitate the control of not only thermal oxidative degradation but also heat-induced trans isomerisation of double bonds in unsaturated lipids. © 2011 Elsevier Ltd. All rights reserved.

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