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Substrate Specificities of GH8, GH39, and GH52 β-xylosidases from Bacillus halodurans C-125 Toward Substituted Xylooligosaccharides
Applied Biochemistry and Biotechnology ( IF 3 ) Pub Date : 2021-01-04 , DOI: 10.1007/s12010-020-03451-2
Koji Teramoto 1 , Sosyu Tsutsui 1, 2 , Tomoko Sato 3 , Zui Fujimoto 3 , Satoshi Kaneko 1, 2
Affiliation  

Substrate specificities of glycoside hydrolase families 8 (Rex), 39 (BhXyl39), and 52 (BhXyl52) β-xylosidases from Bacillus halodurans C-125 were investigated. BhXyl39 hydrolyzed xylotriose most efficiently among the linear xylooligosaccharides. The activity decreased in the order of xylohexaose > xylopentaose > xylotetraose and it had little effect on xylobiose. In contrast, BhXyl52 hydrolyzed xylobiose and xylotriose most efficiently, and its activity decreased when the main chain became longer as follows: xylotetraose > xylopentaose > xylohexaose. Rex produced O-β-D-xylopyranosyl-(1 → 4)-[O-α-L-arabinofuranosyl-(1 → 3)]-O-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranose (Ara2Xyl3) and O-β-D-xylopyranosyl-(1 → 4)-[O-4-O-methyl-α-D-glucuronopyranosyl-(l → 2)]-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranose (MeGlcA2Xyl3), which lost a xylose residue from the reducing end of O-β-D-xylopyranosyl-(1 → 4)-[O-α-L-arabinofuranosyl-(1 → 3)]-O-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranose (Ara3Xyl4) and O-β-D-xylopyranosyl-(1 → 4)-[O-4-O-methyl-α-D-glucuronopyranosyl-(1 → 2)]-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranosyl-(1 → 4)-β-D-xylopyranose (MeGlcA3Xyl4). It was considered that there is no space to accommodate side chains at subsite −1. BhXyl39 rapidly hydrolyzes the non-reducing-end xylose linkages of MeGlcA3Xyl4, while the arabinose branch does not significantly affect the enzyme activity because it degrades Ara3Xyl4 as rapidly as unmodified xylotetraose. The model structure suggested that BhXyl39 enhanced the activity for MeGlcA3Xyl4 by forming a hydrogen bond between glucuronic acid and Lys265. BhXyl52 did not hydrolyze Ara3Xyl4 and MeGlcA3Xyl4 because it has a narrow substrate binding pocket and 2- and 3-hydroxyl groups of xylose at subsite +1 hydrogen bond to the enzyme.



中文翻译:

嗜盐芽孢杆菌C-125对取代的木寡糖的GH8,GH39和GH52β-木糖苷酶的底物特异性

研究了来自嗜碱芽孢杆菌C-125的糖苷水解酶家族8(Rex),39(Bh Xyl39)和52(Bh Xyl52)β-木糖苷酶的底物特异性。在线性木寡糖中,Bh Xyl39最有效地水解了木三糖。活性以木二糖>木二戊糖>木四糖的顺序降低,并且对木二糖几乎没有影响。相反,Bh Xyl52最有效地水解了木糖和木三糖,并且当主链变长时,其活性降低,如下所示:木四糖>木戊糖>木己糖。雷克斯产生O -β-D-吡喃吡喃糖基-(1→4)-[ O -α-L-阿拉伯呋喃糖基-(1→3)]- O-β-D-吡喃喃糖基-(1→4)-β-D-吡喃吡喃糖(Ara 2 Xyl 3)和O -β-D-吡喃吡喃糖基-(1→4)-[ O -4- O-甲基-α- D-葡萄糖醛酸吡喃糖基-(1→2)]-β-D-吡喃木糖基-(1→4)-β-D-吡喃木糖(MeGlcA 2 Xyl 3),其从O - β-D的还原端失去木糖残基-木吡喃糖基-(1→4)-[ O -α-L-阿拉伯呋喃糖基-(1→3)]- O -β-D-木吡喃糖基-(1→4)-β-D-木吡喃糖基-(1→4) -β-D-吡喃木糖(Ara 3 Xyl 4)和O -β-D-吡喃木糖基-(1→4)-[ O -4- O-甲基-α-D-葡糖醛酸吡喃糖基-((1→2)]-β-D-吡喃吡喃糖基-(1→4)-β-D-吡喃吡喃糖基-(1→4)-β-D-吡喃吡喃糖(MeGlcA 3 Xyl 4)。认为在子位点-1没有空间容纳侧链。Bh Xyl39迅速水解MeGlcA 3 Xyl 4的非还原端木糖键,而阿拉伯糖分支不会显着影响酶的活性,因为它与未修饰的木糖一样迅速降解Ara 3 Xyl 4。该模型结构表明,Bh Xyl39通过在葡萄糖醛酸和Lys265之间形成氢键来增强MeGlcA 3 Xyl 4的活性。Bh Xyl52不会水解Ara 3 Xyl 4和MeGlcA 3 Xyl 4,因为它具有狭窄的底物结合口袋,并且木糖的2-和3-羟基在亚位点+1与酶的氢键结合。

更新日期:2021-01-04
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