Research progress in structure and function of pectin methylesterase / 生物工程学报

Pectin methylesterase (PME) is an important pectinase that hydrolyzes methyl esters in pectin to release methanol and reduce the degree of methylation of pectin. At present, it has broad application prospects in food processing, tea beverage, paper making and other production processes. With the in-depth study of PME, the crystal structures with different sources have been reported. Analysis of these resolved crystal structures reveals that PME belongs to the right-hand parallel β-helix structure, and its catalytic residues are two aspartic acids and a glutamine, which play the role of general acid-base, nucleophile and stable intermediate, in the catalytic process. At the same time, the substrate specificity is analyzed to understand the recognition mechanism of the substrate and active sites. This paper systematically reviews these related aspects.

Characterization and structure of a novel thermostable glucoamylase from Talaromyces leycettanus JCM12802 / 生物工程学报

Glucoamylase is a critical ingredient for saccharification in the starch decomposition, and widely used in food, pharmaceutical and fermentation industries. Glucoamylases are usually thermostable and have peak activities at high temperature, as required for the industrial process of glucose production. In this study, a glucoamylase gene belonging to the glycoside hydrolase (GH) family 15, Tlga15A, was cloned from Talaromyces leycettanus JCM12802, and successfully expressed in Pichia pastoris GS115. Recombinant glucoamylase TlGA showed optimal activities at pH 4.5 and 75 °C. The result of thermostability analysis showed that TlGA retained above 70% activity after incubating for 1 h at 65 °C, and 43% residual activity after 30 min at 70 °C. Moreover, TlGA had high resistance to most metal ions and chemical reagents tested. Various starch substrates could be hydrolyzed by TlGA, including soluble starch (255.6±15.3) U/mg, amylopectin (342.3±24.7) U/mg, glycogen (185.4±12.5) U/mg, dextrin (423.3±29.3) U/mg and pullulan (65.7±8.1) U/mg. The primary, secondary and tertiary structures of glucoamylase were further analyzed. The low ratio of Gly in the primary structure and low exposed nonpolarity solvent accessible surface in the tertiary structure may be the main reasons for TlGA's thermostability. These results show that TlGA is great promising for potential use in the commercial production of glucose syrups. Moreover, this research will provide knowledge and innovating ideas for the improvement of glucoamylase thermostability.

A highly active GH11 xylanase from Penicillium sp. L1 with potential applications in xylo-oligosaccharide production / 生物工程学报

Xylanase is a high-profile glycoside hydrolase with applications in brewing, feed, pharmacy and bioenergy industries, but most of xylanases are in active below 30 ℃. In order to obtain low temperature active xylanase, a xylanase gene, XYN11A, was cloned from Penicillium sp. L1 and expressed in Pichia pastoris GS115. After purification and enzyme assay, optimal pH and temperature were determined to be 3.5 to 4.0 and 55 ℃. This enzyme was stable at acid and neutral condition (pH 1.0 to 7.0) or under the treatment of 40 ℃ for 1 hour. This xylanase displayed strong resistance to all tested ions and chemicals. Noteworthily, XYN11A maintained a higher activity of 6 700 U/mg than a lot of GH11 xylanase, and demonstrated higher activity (24% to 58%) at lower temperature from 20 to 40 ℃. After beechwood xylan hydrolysis for 16 h, the hydrolysates consisted mainly of xylobiose, xylotriose and xylotetraose and barely of xylose, thus XYN11A could be used for the production of prebiotic xylooligosaccharide. Possessing the features of acidophilic, highly active at lower temperature and oligosaccharide production, XYN11A demonstrated great potential in food and feed industrials.

A novel bifunctional xylanase/cellulase TcXyn10A from Thermoascus crustaceus JCM12803 / 生物工程学报

Efficient utilization of cellulose and xylan is of importance in the bioethanol industry. In this study, a novel bifunctional xylanase/cellulase gene, Tcxyn10a, was cloned from Thermoascus crustaceus JCM12803, and the gene product was successfully overexpressed in Pichia pastoris GS115. The recombinant protein was then purified and characterized. The pH and temperature optima of TcXyn10A were determined to be 5.0 and 65-70 °C, respectively. The enzyme retained stable under acid to alkaline conditions (pH 3.0-11.0) or after 1-h treatment at 60 °C. The specific activities of TcXyn10A towards beechwood xylan, wheat arabinoxylan, sodium carboxymethyl cellulose and lichenan were (1 480±26) U/mg, (2 055±28) U/mg, (7.4±0.2) U/mg and (10.9±0.4) U/mg, respectively. Homologous modeling and molecular docking analyses indicated that the bifunctional TcXyn10A has a single catalytic domain, in which the substrate xylan and cellulose shared the same binding cleft. This study provides a valuable material for the study of structure and function relationship of bifunctional enzymes.

Antitumor activities of extracts from Stellera chamaejasmel L by various polarity of solvent extraction in vitro / 中国临床药理学与治疗学

AIM: To find the optimal polarity zone by comparing the antitumor effects of various polarity solvent extracts. METHODS: The various polarity solvent was used to separate the plant dry powder (petroleum ether, ethyl acetate,acetone,and ethanol). The antitumor activities of the different extracts on human cancer cell lines in vitro were analyzed using MTT assay. RESULTS : The petroleum ether extract and the ethyl acetate extract strongly inhibited the proliferation of leukemia K562 cells, oesophagus cancer Eca-109 cells and hepato- carcinoma HepG_2 cells, and showed significant dose-dependent response while the acetone extract and the ethanol extract exhibited low antitumor activities in vitro. The petroleum ether extract was the most active part. CONCLUSION: The petroleum ether extract is the principal antitumor extract from Stellera chanraejasmel L.

Therapeutic effects of Zhuyejiao tablets on chronic pelvic inflammation induced by coliform in rats / 中国临床药理学与治疗学

AIM: To investigate the therapeutic effects of Zhuyejiao tablets (Tab.ZYJ) on chronic pelvic inflammation (CPI) induced by coliform in rats. METHODS: The CPI model was made by injecting coliform O-B_4 standard strains in the uterus of rat. Animals were randomly divided into six groups and drugs were administered for 21 days, bid, respectively. The immune function of animals was measured and the uterus was pathologically observed. RESULTS: The level of serum agglutinin and lymphocyte transformation index markedly increased in all ZYJ groups. Morphological investigation also revealed the alleviation of inflammation in ZYJ groups. CONCLUTION: ZYJ has therapeutic effects on chronic pelvic inflammation in rats.

Protective effect of Cistanchis glycosides on ethanol-induced liver damage in mice / 中国临床药理学与治疗学

AIM:To research the protection of Cistanchis glycosides on ethanol-induced liver damage in mice.METHODS:40 mice were divided into 4 groups in random,and administered by gavage for 4 weeks.Cistanchis glycosides were twice a day,ethanol were once a day.When time limit arrived,mice were weighted,the serum was afforded to detect the liver function index,liver homogenate were prepared for biochemical detections,liver remained were fixed for pathological investigation.RESULTS:When mice were damaged by ethanol,liver index,liver function index,contents of TG,TC,MDA and LPO were increased distinctly(P

Comparison of energy metabolism on brain lacking oxygen between Salvia miltiorrhiza Bunge injection and Salvia przewalskii Maxim injection in mice / 中国临床药理学与治疗学

AIM: To compare the influence of salvia miltiorrhiza Bunge njection (SMBI) and salvia przewalskii Maxim injec tion (SPMI) on energy metabolism of acute brain lacking oxygen. METHODS : The whole brain lacking oxygen model was made by injecting NaNO 2 in mice and then wrote down the existent time of mice and detected the contents of Na +-K +-ATPase, Ca 2+ -ATPase and lactic acid (LD) in the brain. RESULTS: SMBI and SPMI both significantly lengthened the existent tim e of mice with the whole brain lacking oxygen, decreased the contents of LD and increased the activity of ATPase in mice. In increasing the activity of ATPase, the influence of SPMI was more than that of SMBI (P 0.05 ). CONCLUSION: SMBI an d SPMI have distinctive protection on energy metabolism of acute brain lacking o xygen. Both of them can lengthen the existent of mice, reduce the contents of LD in brain and increase the activity of ATPase, but SPMI is more excellent than S MBI in increasing the activity of ATPase.