Enzymatic properties and degradation characterization of a bis(2-hydroxyethyl) terephthalate hydrolase from Saccharothrix sp / 生物工程学报

The discovery of new enzymes for poly(ethylene terephthalate) (PET) degradation has been a hot topic of research globally. Bis-(2-hydroxyethyl) terephthalate (BHET) is an intermediate compound in the degradation of PET and competes with PET for the substrate binding site of the PET-degrading enzyme, thereby inhibiting further degradation of PET. Discovery of new BHET degradation enzymes may contribute to improving the degradation efficiency of PET. In this paper, we discovered a hydrolase gene sle (ID: CP064192.1, 5085270-5086049) from Saccharothrix luteola, which can hydrolyze BHET into mono-(2-hydroxyethyl) terephthalate (MHET) and terephthalic acid (TPA). BHET hydrolase (Sle) was heterologously expressed in Escherichia coli using a recombinant plasmid, and the highest protein expression was achieved at a final concentration of 0.4 mmol/L of isopropyl-β-d-thiogalactoside (IPTG), an induction duration of 12 h and an induction temperature of 20 ℃. The recombinant Sle was purified by nickel affinity chromatography, anion exchange chromatography, and gel filtration chromatography, and its enzymatic properties were also characterized. The optimum temperature and pH of Sle were 35 ℃ and 8.0, and more than 80% of the enzyme activity could be maintained in the range of 25-35 ℃ and pH 7.0-9.0 and Co2+ could improve the enzyme activity. Sle belongs to the dienelactone hydrolase (DLH) superfamily and possesses the typical catalytic triad of the family, and the predicted catalytic sites are S129, D175, and H207. Finally, the enzyme was identified as a BHET degrading enzyme by high performance liquid chromatography (HPLC). This study provides a new enzyme resource for the efficient enzymatic degradation of PET plastics.

The analysis of the relationship between the severity of non-alcoholic fatty liver disease and metabolic syndrome / 中国综合临床

Objective To investigate the relationships between the severity of non-alcoholic fatty liver disease (NAFLD) and metabolic syndrome (MS).Methods One hundred and twenty-seven cases of NAFLD patients were selected from March 2011 to August 2012 in the First Hospital Affiliated to Fujian Medical University,of them,61 patients with mild NAFLD,45 patients with moderate and 21 patients with severe.And 21 cases without NAFLD were selected as control group during the same hospitalized period.All objects received the measures of height,body weight,waist circumference (WC),blood pressure; Liver ultrasonic examination,the examination of fasting plasma glucose,blood fat and hepatic function detections were also handed by special people.Results The proportion of overweight in the control group and the three NAFLD subgroups were 57.1％ (12/21),88.5％ (54/61),95.6％ (43/45) and 100％ (21/21) respectively (x2 =18.376,P ＜0.001) ;The proportion of the obesity in control group and the three NAFLD subgroups were 19.0％ (4/21),44.3％ (27/61),64.4％ (29/45) and 71.4％ (15/21) respectively(x2 =16.440,P =0.001).The proportion of the metabolic syndrome of the control group and the three NAFLD subgroups were 14.3％ (3/21),45.9％(28/61),71.1％ (32/45) and 71.4％ (15/21) respectively (x2 =22.637,P ＜ 0.05).All three subgroups of NAFLD were higher than the control group (x2 =6.641,P ＜ 0.05 ; x2 =18.562,P ＜ 0.05 ; x2 =14.000,P ＜0.05,respectively).The severity of NAFLD was positively correlated with BMI,WC,TG,FBG,SBP,and DBP (r =0.467,0.503,0.386,0.369,0.279,0.295,P ＜ 0.01),and negatively correlated with HDL-C (r =-0.209,P ＜0.05).Conclusion The severity of NAFLD had significant correlations with metabolic syndrome's components.