Characterization of highly active tyrosine ammonia lyase and its application in biosynthesis of p-coumaric acid / 生物工程学报

p-coumaric acid is one of the aromatic compounds that are widely used in food, cosmetics and medicine due to its properties of antibacterium, antioxidation and cardiovascular disease prevention. Tyrosine ammonia-lyase (TAL) catalyzes the deamination of tyrosine to p-coumaric acid. However, the lack of highly active and specific tyrosine ammonia lyase limits cost-effective microbial production of p-coumaric acid. In order to improve biosynthesis efficiency of p-coumaric acid, two tyrosine ammonia-lyases, namely Fc-TAL2 derived from Flavobacterium columnare and Fs-TAL derived from Flavobacterium suncheonense, were selected and characterized. The optimum temperature (55 ℃) and pH (9.5) for Fs-TAL and Fc-TAL2 are the same. Under optimal conditions, the specific enzyme activity of Fs-TAL and Fc-TAL2 were 82.47 U/mg and 13.27 U/mg, respectively. Structural simulation and alignment analysis showed that the orientation of the phenolic hydroxyl group of the conserved Y50 residue on the inner lid loop and its distance to the substrate were the main reasons accounting for the higher activity of Fs-TAL than that of Fc-TAL2. The higher activity and specificity of Fs-TAL were further confirmed via whole-cell catalysis using recombinant Escherichia coli, which could convert 10 g/L tyrosine into 6.2 g/L p-coumaric acid with a yield of 67.9%. This study provides alternative tyrosine ammonia-lyases and may facilitate the microbial production of p-coumaric acid and its derivatives.

Imaging signs for predicting hematoma enlargement in patients with intracerebral hemorrhage / 国际脑血管病杂志

Hematoma enlargement is a common harmful event after cerebral hemorrhage, which can lead to deterioration of neurological function and poor outcome. Early detection of high-risk patients can help prevent hematoma enlargement and improve the outcome of patients. Although the exact mechanism of hematoma enlargement is unclear, more and more evidence shows that many imaging signs may be related to hematoma enlargement, such as dot sign, mixed sign, black hole sign, island sign, etc. This article mainly reviews the relevant imaging prediction factors of hematoma enlargement from the perspective of imaging.

Construction and optimization of microbial cell factories for producing cis, cis-muconic acid / 生物工程学报

cis, cis-muconic acid (MA) is an important platform chemical. Now, majority of reported engineered strains are genetically instable, the exogenous genes are expressed under the control of expensive inducer and the components of their fermentation medium are complex, thus large-scale microbial production of MA is limited due to the lack of suitable strains. Hence, it is still necessary to construct novel high-performance strain that is genetically stable, no induction and grows in simple inorganic fermentation medium. In this study, after 3 exogenous genes (aroZ, aroY, catA) for biosynthesis of MA were integrated into previously constructed 3-hydroshikimate producing Escherichia coli WJ060 strain and combinatorially regulated with 3 constitutive promoters with different strengths, 27 engineered strains were constructed. The best engineered strain, E. coli MA30 could produce 1.7 g/L MA in the simple inorganic fermentation medium without induction. To further enhance the production capacity of MA, the mutant library of E. coli MA30 was constructed by genome replication engineering and screened via high-throughput assay. After two-round screening, the new strain, E. coli MA30-G2 with improved production of MA was obtained, and the titer of MA increased more than 8%. Under the condition of 5 L fed-batch fermentation, E. coli MA30-G2 could produce about 11.5 g/L MA. Combinatorial regulation and high-throughput screening provide important reference to microbial production of other bio-based chemicals.

Icariin inhibits orthodontically induced inflammatory root resorption / 中国组织工程研究

BACKGROUND: Icari n as one of the main components of Epimedium has an inhibitory effect on osteoclasts.. OBJECTIVE: To further investigate the influence of icariin on the root absorption of the maxil ary first molar at mesial part during orthodontic treatment in rats. METHODS: Orthodontic root resorption models were established in the left maxil a of rats. Local injection of 200 mg/kg icari n (icari n group) or normal saline (positive control group) was administrated into the left first molar buccal periosteum. The right maxil a of rats served as negative control group that was treated with neither appliance nor drug injection. The mesial distance between bilateral first molars and the contralateral maxil ary incisor was measured before and after the appliance was placed. Mesial surface of the mesial root of bilateral maxil ary first molars was observed using scanning electron microscope. RESULTS AND CONCLUSION: Mesial movement of the maxil ary molars in the icari n group was significantly less than that in the positive control group (P < 0.05). Under the scanning electron microscope, smal absorption lacunae were scattered in the icari n group, while the positive control group showed a large amount of absorption lacunae and they were interconnected into a sheet, showing a stark contrast with the smooth root surface of the negative control group. It is indicated that icari n can inhibit root resorption caused by orthodontic treatment, while reducing the amount of mesial movement of the molar under corrective force.