Enhancing the chemoenzymatic synthesis of arabinosylated xylo-oligosaccharides by GH51 α-l-arabinofuranosidase
摘要:
Random mutagenesis was performed on the alpha-L-arabinofuranosidase of Thermobacillus xylanilyticus in order to enhance its ability to perform transarabinofuranosylation using natural xylo-oligosaccharides as acceptors. To achieve this goal, a two-step, high-throughput digital imaging protocol involving a colorimetric substrate was used to screen a library of 30,000 mutants. In the first step this screen selected for hydrolytically-impaired mutants, and in the second step the screen identified mutants whose global activity was improved in the presence of a xylo-oligosaccharide mixture. Thereby, 199 mutants displaying lowered hydrolytic activity and modified properties were detected. In the presence of these xylo-oligosaccharides, most of the 199 (i.e., 70%) enzymes were less inhibited and some (18) mutants displayed an unambiguous alleviation of inhibition (<25% loss of activity). More precise monitoring of reactions catalyzed by the most promising mutants revealed a significant improvement of the synthesis yields of transglycosylation products (up to 18% compared to 9% for the parental enzyme) when xylobiose was present in the reaction. Genetic analysis of improved mutants revealed that many of the amino acid substitutions that correlate with the modified phenotype are located in the vicinity of the active site, particularly in subsite -1. Consequently, we hypothesize that these mutations modify the active site topology or the molecular interaction network of the L-arabinofuranoside donor substrate, thus impairing the hydrolysis and concomitantly favoring transglycosylation onto natural acceptors. (C) 2014 Elsevier Ltd. All rights reserved.
Expression, Purification and Characterization of a Bifunctional α-<scp>L</scp>-Arabinofuranosidase/β-<scp>D</scp>-Xylosidase from<i>Trichoderma Koningii</i>G-39
cation-exchanged chromatography. The purified enzyme exhibits both a-L-arabinofuranosidase and β-D-xylosidase (Xyl) activities with p-nitrophenyl-a-L-arabionfuranoside (pNPAF) and 2,4-dinitrophenyl-β-D-xylopyanoside (2,4-DNPX) as substrate, respectively. The stability and the catalytic feature of the bifunctional enzyme were characterized. The enzyme was stable for at least 2 h at pH values between 2 and
Synthesis of β-1,4-Linked Galactan Side-Chains of Rhamnogalacturonan I
作者:Mathias C. F. Andersen、Stjepan K. Kračun、Maja G. Rydahl、William G. T. Willats、Mads H. Clausen
DOI:10.1002/chem.201602197
日期:2016.8.8
The synthesis of linear‐ and (1→6)‐branched β‐(1→4)‐d‐galactans, side‐chains of the pectic polysaccharide rhamnogalacturonan I is described. The strategy relies on iterative couplings of n‐pentenyl disaccharides followed by a late stage glycosylation of a common hexasaccharide core. Reaction with a covalent linker and immobilization on N‐hydroxysuccinimide (NHS)‐modified glass surfaces allows the generation
直链的和合成(1→6) -支化的β-(1→4) - d -galactans,鼠李我描述了果胶多糖的侧链。该策略依赖于正戊烯基二糖的迭代偶联,随后是常见六糖核心的晚期糖基化。与共价接头反应并固定在N-羟基琥珀酰亚胺(NHS)修饰的玻璃表面上可以生成碳水化合物微阵列。聚糖阵列能够以高通量的方式研究蛋白质与碳水化合物的相互作用,本文通过mAb和CBM的结合研究证明了这一点。
Araf51 with improved transglycosylation activities: one engineered biocatalyst for one specific acceptor
were selected on their ability to catalyze the transglycosylationreaction of p-nitrophenyl α-L-arabinofuranoside (pNP-Araf) used as a donor and various aliphatic alcohols as acceptors. This screening strategy underlined 5 interesting clones, each one corresponding to one acceptor. They appeared to be much more efficient in the transglycosylationreaction compared to the wild type enzyme whereas no self-condensation
Determination of the absolute configuration of monosaccharides by 1H NMR spectroscopy of their per-O-(S)-2-methylbutyrate derivatives
作者:William S. York、Stephen Hantus、Peter Albersheim、Alan G. Darvill
DOI:10.1016/s0008-6215(97)00050-5
日期:1997.5
Abstract An empirical method was developed to determine the absoluteconfiguration of monosaccharides, based on high-field 1H NMR spectroscopy of their per- O-(S)-2-methylbutyrate (SMB) derivatives. The SMB derivatives of the D and L forms of a given monosaccharide are diastereomers, allowing them to be distinguished on the basis of differences in their 1H NMR chemical shifts. The reproducibility of
Abstract A white-rot fungus Dichomitus squalens , when grown on 1% wheat-straw glucuronoarabinoxylan under aerated submerged conditions, secreted an α- l -arabinofuranosidase (4.3 nkat/mL). The enzyme was purified 70-fold by ammonium sulfate precipitation, chromatofocusing on PBE 94, gel filtration on Ultrogel AcA 54, rechromatofocusing on PBE 94, and lectin affinity chromatography on Concanavalin