Chemo-enzymatic synthesis of 4-methylumbelliferyl β-(1→4)-<scp>d</scp>-xylooligosides: new substrates for β-<scp>d</scp>-xylanase assays
作者:Elena V. Eneyskaya、Dina R. Ivanen、Konstantin A. Shabalin、Anna A. Kulminskaya、Leon V. Backinowsky、Harry Brumer III、Kirill N. Neustroev
DOI:10.1039/b409583a
日期:——
Transglycosylation catalyzed by a β-D-xylosidase from Aspergillus sp. was used to synthesize a set of 4-methylumbelliferyl (MU)
β-1â4-D-xylooligosides having the common structure [β-D-Xyl-(1â4)]2â5-β-D-Xyl-MU. MU xylobioside synthesized chemically by the condensation of protected MU β-D-xylopyranoside with ethyl 2,3,4-tri-O-acetyl-1-thio-β-D-xylopyranoside was used as a substrate for transglycosylation with the β-D-xylosidase from Aspergillus sp. to produce higher MU xylooligosides. The structures of oligosaccharides obtained were established by 1H and 13C NMR spectroscopy and electrospray tandem mass spectrometry. MU β-D-xylooligosides synthesized were tested as fluorogenic substrates for the GH-10 family β-D-xylanase from Aspergillus orizae and the GH-11 family β-D-xylanase I from Trichoderma reesei. Both xylanases released the aglycone from MU xylobioside and the corresponding trioside. With substrates having d.p. 4 and 5, the enzymes manifested endolytic activities, splitting off MU, MUX, and MUX2 primarily.
利用曲霉属(Aspergillus sp.)的δ-D-木糖苷酶催化的转糖基化作用,合成了一组具有共同结构[δ-D-Xyl-(1â4)]2â5-δ-D-Xyl-MU的4-甲基伞形酮(MU)δ-1â4-D-木寡糖苷。以受保护的 MU δ-D-木吡喃糖苷与乙基 2,3,4-三-O-乙酰基-1-硫代-δ-D-木吡喃糖苷缩合合成的 MU xylobioside 为底物,用曲霉属的δ-D-木糖苷酶进行转糖基化,生成更高级的 MU xylooligosides。通过 1H 和 13C NMR 光谱以及电喷雾串联质谱法确定了所获得的低聚糖的结构。合成的 MU δ²-D-xylooligosides 被测试为黑曲霉 GH-10 家族 δ²-D-Xylanase 和毛霉 GH-11 家族 δ²-D-Xylanase I 的荧光底物。这两种木聚糖酶都能从 MU xylobioside 和相应的三苷中释放出琼脂酮。当底物的d.p.为4和5时,酶表现出内溶活性,主要分裂出MU、MUX和MUX2。