Exploring novel non-Leloir β-glucosyltransferases from proteobacteria for modifying linear (β1→3)-linked gluco-oligosaccharide chains
作者:Gudmundur O Hreggvidsson、Justyna M Dobruchowska、Olafur H Fridjonsson、Jon O Jonsson、Gerrit J Gerwig、Arnthor Aevarsson、Jakob K Kristjansson、Delphine Curti、Robert R Redgwell、Carl-Eric Hansen、Johannis P Kamerling、Takoua Debeche-Boukhit
DOI:10.1093/glycob/cwq165
日期:2011.3
Over the years several β-glucan transferases from yeast and fungi have been reported, but enzymes with such an activity from bacteria have not been characterized so far. In this work, we describe the cloning and expression of genes encoding β-glucosyltransferase domains of glycosyl hydrolase family GH17 from three species of proteobacteria: Pseudomonas aeruginosa PAO1, P. putida KT2440 and Azotobacter vinelandii ATCC BAA-1303. The encoded enzymes of these GH17 domains turned out to have a non-Leloir trans-β-glucosylation activity, as they do not use activated nucleotide sugar as donor, but transfer a glycosyl group from a β-glucan donor to a β-glucan acceptor. More particularly, the activity of the three recombinant enzymes on linear (β1 → 3)-linked gluco-oligosaccharides (Lam-Glc4–9) and their corresponding alditols (Lam-Glc4–9-ol) was studied. Detailed structural analysis, based on thin-layer chromatography, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, electrospray ionization mass spectrometry, and 1D/2D 1H and 13C nuclear magnetic resonance data, revealed diverse product spectra. Depending on the enzyme used, besides (β1 → 3)-elongation activity, (β1 → 4)- or (β1 → 6)-elongation, or (β1 → 6)-branching activities were also detected.
多年来,酵母和真菌中的β-葡聚糖转移酶已被报道,但细菌中具有这种活性的酶迄今尚未被鉴定。在这项工作中,我们描述了三种蛋白细菌中编码糖基水解酶家族 GH17 β-葡聚糖转移酶结构域的基因的克隆和表达:铜绿假单胞菌(Pseudomonas aeruginosa PAO1)、腐生假单胞菌(P. putida KT2440)和乙烯绿氮菌(Azotobacter vinelandii ATCC BAA-1303)。这些 GH17 结构域编码的酶具有非 Leloir 反式-β-葡萄糖基化活性,因为它们不使用活化的核苷酸糖作为供体,而是将一个糖基从β-葡聚糖供体转移到β-葡聚糖受体。更具体地说,研究了这三种重组酶对线性(β1 → 3)连接的葡聚寡糖(Lam-Glc4-9)及其相应的醛醇(Lam-Glc4-9-ol)的活性。基于薄层色谱法、基质辅助激光解吸电离飞行时间质谱法、电喷雾电离质谱法以及 1D/2D 1H 和 13C 核磁共振数据的详细结构分析揭示了不同的产物光谱。根据所用酶的不同,除了(β1 → 3)-伸长活性外,还检测到(β1 → 4)-或(β1 → 6)-伸长或(β1 → 6)-分支活性。