Overexpression and characterization of a thermostable β-agarase producing neoagarotetraose from a marine isolate Microbulbifer sp.AG1

An agarase gene containing 1 302 bp was cloned from Microbulbifer sp. AG1. It encoded a mature protein of 413 amino acids plus a 20-residue signal peptide. The recombinant enzyme without the signal peptide was expressed and purified from Escherichia coli BL21(DE3). When agarose was used as a substrate, the optimal temperature and pH for the enzyme were 60℃ and 7.5, respectively. The recombinant agarase showed excellent thermostability with 67% and 19% of residual activities after incubation at 50℃ and 60℃ for 1 h, respectively.Except SDS, the recombinant agarase had a relatively good resistance against the detected inhibitors, detergents and urea denaturant. Thin layer chromatography analysis and enzyme assay using p-nitrophenyl-α/β-Dgalactopyranoside revealed that the recombinant agarase was a β-agarase that degraded agarose into neoagarotetraose as the main end product. The enzymatic hydrolysis products with different degree of polymerization exhibited the antioxidant activities.

Substitution of His260 residue alters the thermostability of Pseudoalteromonas carrageenovora arylsulfatase

This study aimed to improve the thermostability of arylsulfatase from Pseudoalteromonas carrageenovora. A library of P. carrageenovora arylsulfatase mutants was constructed by introducing random mutagenesis using error-prone PCR. After screening, two mutants of H260L and D84A/H260L showed enhanced thermal stability than the wild-type predecessor (WT). Site-directed mutagenesis demonstrated that only amino acid residue at Position 260 plays an important role in the thermostability of P. carrageenovora arylsulfatase. Thermal inactivation analysis showed that the half-life (t1/2) values at 55°C for H260L, H260I, H260Q, H260F and H260R were 40.6, 48.4, 30.9, 29.1 and 34.5 min, respectively, while that of WT was 9.1 min. Structure modeling demonstrated that the additional hydrogen bonds and/or optimization of surface charge-charge interactions could be responsible for the increased thermostability imparted by H260L, H260I, H260Q, H260F and H260R.

Propofol Attenuates a-Synuclein Aggregation and Neuronal Damage in a Mouse Model of Ischemic Stroke

a-Synuclein is a soluble monomer abundant in the central nervous system. Aggregates of a-synuclein,consisting of higher-level oligomers and insoluble fibrils,have been observed in many chronic neurological diseases and are implicated in neurotoxicity and neurodegeneration.a-Synuclein has recently been shown to aggregate following acute ischemic stroke, exacerbating neuronal damage.Propofol is an intravenous anesthetic that is commonly used during intravascular embolectomy following acute ischemic stroke. While propofol has demonstrated neuroprotective properties following brain injury, the mechanism of protection in the setting of ischemic stroke is unclear. In this study, propofol administration significantly reduced the neurotoxic aggregation of a-synuclein, decreased the infarct area, and attenuated the neurological deficits after ischemic stroke in a mouse model. We then demonstrated that the propofol-induced reduction of a-synuclein aggregation was associated with increased mammalian target of rapamycin/ribosomal protein S6 kinase beta-1 signaling pathway activity and reduction of the excessive autophagy occurring after acute ischemic stroke.

响应面法优化纤维素酶辅助从泡叶藻中提取泡叶藻聚糖的工艺

通过单因素实验研究纤维素酶辅助提取泡叶藻聚糖时液料比、酶添加量、酶解温度、酶解时间等关键因素对泡叶藻聚糖提取率的影响,并进一步采用Box-Behnken实验设计和响应面分析法优化其工艺参数.结果表明,纤维素酶辅助提取泡叶藻聚糖的优化工艺条件为液料比30 mL/g、酶浓度200 IU/mL、酶解时间2.0 h、酶解温度50℃,该条件下多糖提取率为14.65%±0.73%,与模型预测值14.75%非常接近,采用响应面法对泡叶藻聚糖提取条件进行优化合理可行.

Propofol Protects Regulatory T Cells, Suppresses Neurotoxic Astrogliosis, and Potentiates Neurological Recovery After Ischemic Stroke

Dear Editor,Emergency intravascular thrombectomy is the best treatment for acute ischemic stroke [1]. However, it is controversial whether the use of general anesthesia during emergency intravascular thrombectomy affects patient recovery.