Li Qi,Wu Tao,Qi Zhipeng,Zhao Linguo,Pei Jianjun,Tang Feng
Background β-D-xylosidase is a vital exoglycosidase with the ability to hydrolyze xylooligosaccharides to xylose and to biotransform some saponins by cleaving outer β-xylose. β-D-xylosidase is widely used as one of the xylanolytic enzymes in a diverse range of applications, such as fuel, food and the pharmaceutical industry; therefore, more and more studies have focused on the thermostable and xylose-tolerant β-D-xylosidases.Results A thermostable β-xylosidase gene (xln-DT) of 1509 bp was cloned from Dictyoglomus thermophilum and expressed in E.coli BL21. According to the amino acid and phylogeny analyses, the β-xylosidase Xln-DT is a novel β-xylosidase of the GH family 39. The recombinant β-xylosidase was purified, showing unique bands on SDS-PAGE, and had a protein molecular weight of 58.7 kDa. The β-xylosidase Xln-DT showed an optimal activity at pH 6.0 and 75 °C, with p-nitrophenyl-β-D-xylopyranoside (pNPX) as a substrate. Xln-DT displayed stability over a pH range of 4.0-7.5 for 24 h and displayed thermotolerance below 85 °C. The values of the kinetic parameters K
m
and V
max
for pNPX were 1.66 mM and 78.46 U/mg, respectively. In particular, Xln-DT displayed high tolerance to xylose, with 60% activity in the presence of 3 M xylose. Xln-DT showed significant effects on the hydrolyzation of xylobiose. After 3 h, all the xylobiose tested was degraded into xylose. Moreover, β-xylosidase Xln-DT had a high selectivity for cleaving the outer xylose moieties of natural saponins, such as notoginsenoside R1 and astragaloside IV, which produced the ginsenoside Rg1 with stronger anti-fatigue activity and produced cycloastragenol with stronger anti-aging activity, respectively.Conclusion This study provides a novel GH 39 β-xylosidase displaying extraordinary properties of highly catalytic activity at temperatures above 75 °C, remarkable hydrolyzing activity of xylooligosaccharides and rare saponins producing ability in the pharmaceutical and commercial industries.
Jintao Liang,Xiaohang Shi,Huafu Feng,Min Chen,Wenzhan Li,Junxiang Lai,Weipeng Hu,Guiyin Li
In this paper, a novel silicon-based light-addressable potentiometric sensor (LAPS) has been designed for the detection of 1,5-anhydroglucitol (1,5-AG) in human serum. Reduced graphene oxide-chitosan-ferrocene (RGO-CS-Fc)/AuNPs nanohybrids and pyranose oxidase (PROD) enzyme is used to fabricate biological sensitive membrane unit by layer-by-layer assembly technology. When a bias voltage is provided to the LAPS system, the catalytic oxidation reaction between 1,5-AG and PROD to produce H 2 O 2 . The by-product H 2 O 2 can oxidize Fc(Fe 2+ ) ions in RGO-CS-Fc nanohybrids into Fc(Fe 3+ ) ions, which cause the potential of the sensitive membrane surface to change and the potential shift of I-V curve will generate a corresponding offset response. Under the optimal conditions, the potential shift of the LAPS is linearly related to the concentration of 1,5-AG at 10 µg·mL −1 –350 µg·mL −1 with the correlation coefficient of 0.97414. The sensitivity is 0.44273 mV/µg·mL −1 and the lowest detection limit is 10 µg·mL −1 . In addition, the biosensor showed good specificity, acceptable stability and satisfactory recovery rates (91.28%-107.66%), which would be a potential testing methods in actual clinical samples.
1-O-(4-hydroxymethylphenyl)-α-L-rhamnopyranoside (MPG) is a phenolic glycoside that exists in Moringa oleifera seeds with various health benefits, whereas its hepatoprotective effect is lacking clarification. Herein, MPG was isolated from Moringa oleifera seeds, and its hepatoprotection against CCl 4 -induced hepatotoxicity in L02 cells and ICR mice was investigated. Toxicity studies showed that MPG did not induce significant changes in organ coefficients and histological analysis, as well as exhibited no cytotoxicity. In vitro studies indicated that MPG substantially increased cell viability and intracellular SOD activities, and significantly inhibited LDH leakage in CCl 4 -treated cells. In vivo studies demonstrated that MPG significantly alleviated CCl 4 -induced hepatotoxicity in mice, as indicated by diagnostic indicators of hepatic injury, as well as the histopathological analysis. Moreover, MPG reduced the lipid peroxidation levels and regulated the inflammatory cytokines. Notably, MPG substantially suppressed the significant elevation of ROS production in hepatocytes of mice intoxicated with CCl 4 . Moreover, TUNEL assay demonstrated that MPG obviously inhibited hepatic apoptosis induced by CCl 4 . Altogether, these results suggested that MPG has excellent liver-protecting effects against hepatocytotoxicity induced by CCl 4 in mice and L02 cells, which can be further developed as a valuable functional food additive or drug for the treatment of hepatic injury.
危险品化学品经营许可证（带存储）