Gang Ding

Characterization of a novel arabinose-tolerant α-L-arabinofuranosidase with high ginsenoside Rc to ginsenoside Rd bioconversion productivity.

(i) To investigate the enzymatic characterization of α‐l‐arabinofuranosidase from Thermotoga thermarum DSM5069. (ii) To evaluate the performance of its excellent properties on converting ginsenoside Rc to ginsenoside Rd.

High-level expression of recombinant thermostable β-glucosidase in Escherichia coli by regulating acetic acid

In the fermentation progress, fermentation parameters including the feed rate, induction temperature, and induction pH evidently regulate the accumulation of acetic acid generated by recombinant E. coli in the medium. The production of thermostable β-glucosidase (Tpebgl3) was increased by optimizing the parameters mentioned step by step. The optimal conditions were obtained with the highest enzyme expression (560.4U/mL) and the maximum DCW (65g/L) at the pre-induction specific growth rate of 0.2h-1 followed by a post-induction specific growth rate (0.18h-1); induction temperature is 39°C; the pH is 7.2; the concentration of acetic acid was maintained all along below 0.9g/L. Results show it is necessary for the synthesis of Tpebgl3 to regulate the accumulation of acetic acid at the premise of feeding to meet the normal growth of E. coli. The production of Tpebgl3 by recombinant E. coli is the highest reported to date.

Seasonal variation of pheophorbide a and flavonoid in different organs of two Carpinus species and its correlation with immunosuppressive activity

The genus Carpinus of Betulaceae is the most widely distributed in the European landscape. This study reports a comparative study based on the pheophorbide a and flavonoid content from the two main species of the genus Carpinus, Carpinus betulus and Carpinus turczaninowii, respectively, in Nanjing, China. The pheophorbide a and flavonoid content depends on the organ, species, and season. HPLC analysis showed that the pheophorbide a and flavonoid levels were the highest in May and June, respectively, from the leaves of C. betulus ‘Fastigiata.’ In contrast, the content of pheophorbide a and flavonoid in the stems of C. betulus ‘Fastigiata’ or in other species was low. The immunosuppressive effects of the ethyl acetate extracts and methanol extracts from the two Carpinus species were also evaluated. The ethyl acetate extracts of C. betulus ‘Fastigiata’ in May and the methanol extracts of C. betulus ‘Fastigiata’ in June showed better immunosuppressive activity than in other seasons, which coincided with the content of pheophorbide a and flavonoid, respectively. Our findings indicated that C. betulus ‘Fastigiata’ can serve as a medicinal plant against inflammation because of its pheophorbide a and flavonoid content.

B-factor-saturation mutagenesis as a strategy to increase the thermostability of α-L-rhamnosidase from Aspergillus terreus

The α-L-Rhamnosidase is an important enzyme with applications in the food and pharmaceutical industries because it can release terminal L-rhamnose residues from various natural products. In this study, the B-factor-saturation mutagenesis strategy was used to increase the thermostability of α-L-rhamnosidase from Aspergillus terreus. The D594Q and G827K/D594Q mutant enzymes were obtained by screening a series of mutants; they prolonged the half-life of the enzyme at 70 °C by 2.1-fold and 2.3-fold, respectively. Analysis of the 3D structure showed that in the thermostable variants the number of hydrogen bonds and salt bridges was increased, explaining the enhanced thermostability. Kinetic studies showed that the KM values for the D594Q and G827K/D594Q mutant enzymes decreased by 4.0% and 3.8%, respectively. Additionally, the kcat/KM values for the D594Q and G827K/D594Q mutant enzymes increased by 15.5% and 9.2%, respectively. Moreover, the D594Q and G827K/D594Q mutant enzymes exhibited markedly improved isoquercitrin yield at 70 °C that increased by 13.5% and 11.0%, respectively. Therefore, the D594Q and G827K/D594Q mutant enzymes are more suitable for the industrial processes of isoquercitrin preparation.

Characterization of a α-l-rhamnosidase from Bacteroides thetaiotaomicron with high catalytic efficiency of epimedin C

In this study, a α-l-rhamnosidase gene from Bacteroides thetaiotaomicron VPI-5482 was cloned and expressed in Escherichia coli. The specific activity of rhamnosidase was 0.57 U/mg in LB medium with 0.1 mM Isopropyl β-d-Thiogalactoside (IPTG) induction at 28 °C for 8 h. The protein was purified by Ni-NTA affinity, which molecular weight approximately 83.3 kDa. The characterization of BtRha was determined. The optimal activity was at 55 °C and pH 6.5. The enzyme was stable in the pH range 5.0-8.0 for 4 h over 60%, and had a 1-h half-life at 50 °C. The Kcat and Km for p-nitrophenyl-α-l-rhamnopyranoside (pNPR) were 1743.29 s-1 and 2.87 mM, respectively. The α-l-rhamnosidase exhibited high selectivity to cleave the α-1,2 and α-1,6 glycosidic bond between rhamnoside and rhamnoside, rhamnoside and glycoside, respectively, which could hydrolyze rutin, hesperidin, epimedin C and 2″-O-rhamnosyl icariside II. Under the optimal conditions, BtRha transformed epimedin C (1 g/L) to icariin by 90.5% in 4 h. This study provides the first demonstration that the α-l-rhamnosidase could hydrolyze α-1,2 glycosidic bond between rhamnoside and rhamnoside.

Identification of Human Acetylcholinesterase Inhibitors from the Constituents of EGb761 by Modeling Docking and Molecular Dynamics Simulations

AIM AND OBJECTIVE EGb761, a standardized and well-defined product extract of Ginkgo biloba leaves, has beneficial role in the treatment of multiple diseases, particularly Alzheimers disease (AD). Identification of natural acetylcholinesterase (AChE) inhibitors from EGb761 would provide a novel therapeutic approach against the Alzheimers disease. MATERIAL AND METHOD A series of 21 kinds of promising EGb761 compounds were selected, and subsequently evaluated for their potential ability to bind AChE enzyme by molecular docking and a deep analysis of protein surface pocket features. RESULTS Docking results indicated that these compounds can bind tightly with the active site of human AChE, with favorable distinct interactions around several important residues Asp74, Leu289, Phe295, Ser293, Tyr341, Trp286 and Val294 in the active pocket. Most EGB761 compounds could form the hydrogen bond interactions with the negatively charged Asp74 and Phe295 residues. Among these compounds, diosmetin is the one with the best-predicted docking score while three key hydrogen bonds can be formed between small molecule and corresponding residues of the binding site. Besides, other three compounds luteolin, apigenin, and isorhamnetin have better predicted docking scores towards AChE than other serine proteases, i.e. Elastase, Tryptase, Factor XA, exhibiting specificity for AChE inhibition. The RMSD and MM-GBSA results from molecular dymamic simulations indicated that the docking pose of diosmetin-AChE complex displayed highly stable, which can be used for validating the accuracy of molecular docking study. Subsequently, the AChE inhibitory activities of these compounds were evaluated by the Ellmans colorimetric method. CONCLUSION The obtained results revealed that all the four compounds exhibited modest AChE inhibitory activity, among which Diosmetin manifested remarkable anti-AChE activity, comparable with the reference compound, Physostigmine. It can be deduced that these EGB761 compounds can be regarded as a promising starting point for developing AChE inhibitors against AD.

Biotransformation of Ginsenosides Re and Rg1 into Rg2 and Rh1 by Thermostable β-Glucosidase from Thermotoga thermarum

The recombinant thermostable β-glucosidase from Thermotoga thermarum DSM 5069T exhibited high selectivity to catalyze the conversion of ginsenoside Re and Rg1 to the more pharmacologically active minor ginsenoside Rg2 and Rh1, respectively. At a concentration of 1.36 U/mL of the enzyme, a temperature of 85°C, and pH 5.5, 10 g/L ginsenoside Re was transformed into 8.02 g/L Rg2 within 60 min, and 2 g/L ginsenoside Rg1 was transformed into 1.56 g/L Rh1 within 60 min. This paper provides the first report on the production of ginsenoside Rg2 and Rh1 by a highly thermostable β-glucosidase.

The Synergistic Beneficial Effects of Ginkgo Flavonoid and Coriolus versicolor Polysaccharide for Memory Improvements in a Mouse Model of Dementia

This study reports the combination of Ginkgo flavonoid (GF) and Coriolus versicolor polysaccharide (CVP) in the prevention and treatment of a mouse model of Alzheimers disease (AD). GF is a traditional health product, and CVP is the main active ingredient of the medicinal fungus Coriolus versicolor. The Morris water maze test, the Y maze, and the step-through test showed that the combinational use of CVP and GF synergistically improved memory in a mouse model of AD. Based on H&E staining analysis, the combination of CVP and GF decreased the severity of the pathological findings in the brain. Given that the expression of IL-1β, IL-6, and TNF-α was downregulated, the inflammation response in AD mice was considered to be inhibited. The downregulation of GFAP further demonstrated that inflammation was reduced in the brain of AD mice following treatment. Moreover, the expression levels of superoxide dismutase (SOD) and catalase (CAT) were elevated in the brains of treated mice, indicating that oxidation levels were reduced upon the combination treatment. Our results provide new insights into the efficient utilization of traditional medicine for preventing dementia.