Yu-Xue Hou,Shi-Wei Sun,Yang Liu,Yan Li,Xiao-Hong Liu,Wei Wang,Shuang Zhang,Wei Wang
Butein (3,4,2′,4′-tetrahydroxychalcone) belongs to the chalcone family of flavonoids and possesses various biological activities. In this study, butein was synthesized through aldol condensation catalyzed by thionyl chloride (SOCl2)/ethyl alcohol (EtOH) for the first time. The optimal reaction conditions including the molar ratio of reactants, the dosage of catalyst, and the reaction time on the yield of product were investigated, and the straightforward strategy assembles the yield of butein up to 88%. Butein has been found to inhibit xanthine oxidase (XO) activity. Herein, the inhibitory mechanism of butein against XO was discussed in aspects of inhibition kinetic, fluorescence titration, synchronous fluorescence spectroscopy, and molecular docking. The inhibition kinetic analysis showed that butein possessed a stronger inhibition on XO in an irreversible competitive manner with IC50value of 2.93 × 10−6mol L−1. The results of fluorescence titrations and synchronous fluorescence spectroscopy indicated that butein was able to interact with XO at one binding site, and the fluorophores of XO were placed in a more hydrophobic environment with the addition of butein. Subsequently, the result of molecular docking between butein and XO protein revealed that butein formed hydrogen bonding with the amino acid residues located in the hydrophobic cavity of XO. All the results suggested that the inhibitory mechanism of butein on XO may be the insertion of butein into the active site occupying the catalytic center of XO to avoid the entrance of xanthine and inducing conformational changes in XO.Keywords:butein;SOCl2/EtOH;xanthine oxidase;inhibitory mechanism;kinetic analysis;florescence spectroscopy;molecular docking
Zhimin Zhou,Renkuan Li,Tzi Bun Ng,Yunyun Lai,Jie Yang,Xiuyun Ye
Aflatoxin B1(AFB1) is a known toxic human carcinogen and can be detoxified by laccases, which are multicopper oxidases that convert several environmental pollutants and toxins. In this study, a new laccase that could catalyze AFB1degradation was purified and identified from the white-rot fungusCerrena unicolor6884. The laccase was purified using (NH4)2SO4precipitation and anion exchange chromatography, and then identified as Lac 2 through zymogram and UHPLC-MS/MS based on the Illumina transcriptome analysis ofC. unicolor6884. Six putative laccase protein sequences were obtained via functional annotation. Thelac 2cDNA encoding a full-length protein of 512 amino acids was cloned and sequenced to expand the fungus laccase gene library for AFB1detoxification. AFB1degradation by Lac 2 was conducted in vitro at pH 7.0 and 45 °C for 24 h. The half-life of AFB1degradation catalyzed by Lac 2 was 5.16 h. Acetosyringone (AS), Syrinagaldehyde (SA) and [2,2′ -azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS) at 1 mM concentration seemed to be similar mediators for strongly enhancing AFB1degradation by Lac 2. The product of AFB1degradation catalyzed by Lac 2 was traced and identified to be Aflatoxin Q1(AFQ1) based on mass spectrometry data. These findings are promising for a possible application of Lac 2 as a new aflatoxin oxidase in degrading AFB1present in food and feeds.Keywords:laccase;Cerrena unicolor;aflatoxin B1;biodegradation;detoxification;product;transcriptomeKey Contribution:A product identified to be AFQ1was found from Lac 2-mediated AFB1degradation, indicating that AFB1would be transformed during Lac 2-mediated AFB1degradation.
危险品化学品经营许可证（带存储）