Linares-Pastén Javier A, Falck Peter, Albasri Khalil, Kjellström Sven, Adlercreutz Patrick, Logan Derek T, Karlsson Eva Nordberg
Biotechnology, Department of Chemistry, Lund University, Sweden.
Biochemistry and Structural Biology, Department of Chemistry, Lund University, Sweden.
FEBS J. 2017 Jul;284(13):2019-2036. doi: 10.1111/febs.14101. Epub 2017 Jun 18.
Arabinofuranosidases degrade arabinose-containing oligo and polysaccharides, releasing l-arabinose, which is a potentially useful sugar, shown to reduce glycemic response under certain conditions. Arabinofuranosidases (Arafs) are frequently found in GH43, one of the most common GH-families encoded in genomes in gut microbiota, and hence it is of interest to increase understanding of the function of these enzymes in species occurring in the gut. Here we have produced, characterized and solved the three-dimensional structures, at 1.9 and 2.0 Å resolution respectively, of two homologous GH43 enzymes, classified under subfamily 26, from Lactobacillus brevis DSM1269 (LbAraf43) and Weissella strain 142 (WAraf43), respectively. The enzymes, with 74% sequence identity to each other, are composed of a single catalytic module with a β-propeller structure typical of GH43, and an active-site pocket with three identifiable subsites (-1, +1, and +2). According to size exclusion chromatography, native WAraf43 is a dimer, while LbAraf43 is a tetramer in solution. Both of them show activity with similar catalytic efficiency on 1,5-α-l-arabinooligosaccharides with a degree of polymerization (DP) of 2-3. Activity is restricted to substrates of low DP, and the reason for this is believed to be an extended loop at the entrance to the active site, creating interactions in the +2 subsite.
Structural data are available in the PDB under the accession numbers 5M8B (LbAraf43) and 5M8E (WAraf43).
阿拉伯呋喃糖苷酶可降解含阿拉伯糖的寡糖和多糖，释放出L-阿拉伯糖，这是一种潜在有用的糖，在某些条件下已显示可降低血糖反应。阿拉伯呋喃糖苷酶（Arafs）常见于GH43家族，它是肠道微生物群基因组中编码的最常见的GH家族之一，因此，进一步了解这些酶在肠道中存在的物种中的功能很有意义。在这里，我们分别以1.9 Å和2.0 Å的分辨率，制备、表征并解析了来自短乳杆菌DSM1269（LbAraf43）和魏斯氏菌菌株142（WAraf43）的两种同源GH43酶的三维结构，它们分别归类于第26亚家族。这两种酶彼此具有74%的序列同一性，均由一个具有GH43典型β-螺旋桨结构的单一催化模块和一个带有三个可识别亚位点（-1、+1和+2）的活性位点口袋组成。根据尺寸排阻色谱法，天然WAraf43是二聚体，而LbAraf43在溶液中是四聚体。它们对聚合度（DP）为2-3的1,5-α-L-阿拉伯寡糖均具有相似的催化效率。活性仅限于低DP的底物，据信其原因是活性位点入口处的一个延伸环，在+2亚位点产生相互作用。
结构数据可在蛋白质数据库（PDB）中获取，登录号分别为5M8B（LbAraf43）和5M8E（WAraf43）。
