Molecular mechanism of Chuanxiong Rhizoma in treating coronary artery diseases.

Objective: Most of the studies on the herb Chuanxiong Rhizoma (CR) have focused on the l-arginine-nitric oxide (NO) pathway, but the nitrate-nitrite-NO (NO3 --NO2 --NO) pathway was rarely investigated. Therefore, the aim of this study was to evaluate the effects and mechanisms of action of CR in coronary artery disease (CAD). Methods: The NO3 -, NO2 - and NO levels were examined in the NO3 --NO2 --NO pathway. High-performance ion chromatography was used to quantify NO3 - and NO2 - levels. Then, NO was quantified using a multifunctional enzyme marker with a fluorescent probe. The tension of aortic rings was measured using a multi myograph system. Results: High content of NO3 - and low content of NO2 - was found in CR, and which could potently convert NO3 - to NO2 - in the presence of endogenous reductase enzyme. Incubating human coronary artery endothelial cells (HCAECs) with CR-containing serum showed that CR significantly decreased the NO3 - content and increased the levels of NO2 - and NO in the cells under hypoxic conditions. In addition, CR significantly relaxed isolated aortic rings when the l-arginine -NO pathway was blocked. The optimal concentration of CR for relaxation was 200 mg/mL. Conclusion: CR supplements large amounts of NO in cells and vessels to achieve relaxation via the NO3 --NO2 --NO pathway, thereby making up for the deficiency caused by the lack of NO after the l-arginine-NO pathway is suppressed. This study also supports the potential use of a traditional Chinese herb for future drug development.

Simultaneous Enhancement of Thermostability and Catalytic Activity of a Metagenome-Derived ß-Glucosidase Using Directed Evolution for the Biosynthesis of Butyl Glucoside.

Butyl glucoside synthesis using bioenzymatic methods at high temperatures has gained increasing interest. Protein engineering using directed evolution of a metagenome-derived ß-glucosidase of Bgl1D was performed to identify enzymes with improved activity and thermostability. An interesting mutant Bgl1D187 protein containing five amino acid substitutions (S28T, Y37H, D44E, R91G, and L115N), showed catalytic efficiency (kcat/Km of 561.72 mM-1 s-1) toward ρ-nitrophenyl-ß-d-glucopyranoside (ρNPG) that increased by 23-fold, half-life of inactivation by 10-fold, and further retained transglycosidation activity at 50 °C as compared with the wild-type Bgl1D protein. Site-directed mutagenesis also revealed that Asp44 residue was essential to ß-glucosidase activity of Bgl1D. This study improved our understanding of the key amino acids of the novel ß-glucosidases and presented a raw material with enhanced catalytic activity and thermostability for the synthesis of butyl glucosides.

Identification and molecular characterization of a psychrophilic GH1 ß-glucosidase from the subtropical soil microorganism Exiguobacterium sp. GXG2.

The products of bacterial ß-glucosidases with favorable cold-adapted properties have industrial applications. A psychrophilic ß-glucosidase gene named bglG from subtropical soil microorganism Exiguobacterium sp. GXG2 was isolated and characterized by function-based screening strategy. Results of multiple alignments showed that the derived protein BglG shared 45.7% identities with reviewed ß-glucosidases in the UniProtKB/Swiss-Prot database. Functional characterization of the ß-glucosidase BglG indicated that BglG was a 468 aa protein with a molecular weight of 53.2 kDa. The BglG showed the highest activity in pH 7.0 at 35 °C and exhibited consistently high levels of activity within low temperatures ranging from 5 to 35 °C. The BglG appeared to be a psychrophilic enzyme. The values of Km, Vmax, kcat, and kcat/Km of recombinant BglG toward ρNPG were 1.1 mM, 1.4 µg/mL/min, 12.7 s-1, and 11.5 mM/s, respectively. The specific enzyme activity of BglG was 12.14 U/mg. The metal ion of Ca2+ and Fe3+ could stimulate the activity of BglG, whereas Mn2+ inhibited the activity. The cold-adapted ß-glucosidase BglG displayed remarkable biochemical properties, making it a potential candidate for future industrial applications.

BaiJiu Increases Nitric Oxide Bioactivity of Chinese Herbs Used to Treat Coronary Artery Disease Through the NO3--NO2--NO Pathway.

BaiJiu (BJ) is a type of Chinese rice wine combined with the traditional Chinese herbs GuaLou (GL) and XieBai (XB), which have been used to treat and prevent coronary artery disease for nearly 2000 years in China. However, the mechanisms behind the compatibility of the components of this compound (GLXBBJ) have not been deeply investigated. In this study, the compatibility of the GLXBBJ compounds with nitric oxide (NO) bioactivity was evaluated in herbs, cells, and isolated aortic rings. Nitrate (NO3) and nitrite (NO2) concentrations were quantified by the Griess method. Nitric oxide (NO) was quantified by a multifunctional enzyme marker using a fluorescent probe. Qualitative analysis of L-arginine-endothelial NO synthase (eNOS) was performed by Western blotting. The tension of aortic rings was measured by multimyograph system. The ability of BJ to reduce NO3 to NO2 and NO2 to NO was strongest under hypoxic conditions and was not affected by temperature. BJ-containing serum significantly decreased the NO3 content and increased the NO2 content in hypoxic cells. Combining BJ with GL, XB, or GLXB resulted in stronger vasodilation effects. These results demonstrate that BJ effectively reduces NO3/NO2, although only a small amount of NO3 is present. Once combined with GL, XB, or GLXB, which are rich in NO3/NO2, robust NO bioactivity was generated through the NO3-NO2-NO pathway. Therefore, this study supports the potential of using traditional Chinese herbs for promoting medical innovation and for future drug development.

Identification of a metagenome-derived prephenate dehydrogenase gene from an alkaline-polluted soil microorganism.

A novel prephenate dehydrogenase gene designated pdhE-1 was cloned by sequence-based screening of a plasmid metagenomic library from uncultured alkaline-polluted microorganisms. The deduced amino acid sequence comparison and phylogenetic analysis indicated that PdhE-1 and other putative prephenate dehydrogenases were closely related. The putative prephenate dehydrogenase gene was subcloned into pETBlue-2 vector and overexpressed in Escherichia coli BL21(DE3) pLacI. The recombinant protein was purified to homogeneity. The maximum activity of the PdhE-1 protein occurred at pH 8.0 and 45 °C using prephenic acid as the substrate. The prephenate dehydrogenase had an apparent K m value of 0.87 mM, a V max value of 41.5 U/mg, a k cat value of 604.8/min and a k cat/K m value of 1.16 × 10(4)/mol/s. L-Tyrosine did not obviously inhibit the recombinant PdhE-1 protein. The identification of a metagnome-derived prephenate dehydrogenase provides novel material for studies and application of proteins involved in tyrosine biosynthesis.