Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan.
Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki, 305-8568, Japan.
Appl Microbiol Biotechnol. 2020 Jan;104(1):201-210. doi: 10.1007/s00253-019-10244-z. Epub 2019 Nov 28.
Aspergillus oryzae produces hydrolases involved in xyloglucan degradation and induces the expression of genes encoding xyloglucan oligosaccharide hydrolases in the presence of xyloglucan oligosaccharides. A gene encoding α-xylosidase (termed AxyA), which is induced in the presence of xyloglucan oligosaccharides, is identified and expressed in Pichia pastoris. AxyA is a member of the glycoside hydrolase family 31 (GH31). AxyA hydrolyzes isoprimeverose (α-D-xylopyranosyl-(1→6)-D-glucopyranose) into D-xylose and D-glucose and shows hydrolytic activity with other xyloglucan oligosaccharides such as XXXG (heptasaccharide, GlcXyl) and XLLG (nonasaccharide, GlcXylGal). Isoprimeverose is a preferred AxyA substrate over other xyloglucan oligosaccharides. In the hydrolysis of XXXG, AxyA releases one molecule of D-xylose from one molecule of XXXG to yield GXXG (hexasaccharide, GlcXyl). AxyA does not contain a signal peptide for secretion and remains within the cell. The intracellular localization of AxyA may help determine the order of hydrolases acting on xyloglucan oligosaccharides.
米曲霉产生参与木葡聚糖降解的水解酶，并在木葡聚糖寡糖存在的情况下诱导编码木葡聚糖寡糖水解酶的基因表达。鉴定并在巴斯德毕赤酵母中表达了一种在木葡聚糖寡糖存在下诱导的α-木糖苷酶（称为 AxyA）基因。AxyA 是糖苷水解酶家族 31（GH31）的成员。AxyA 将异海藻糖（α-D-吡喃木糖基-(1→6)-D-吡喃葡萄糖）水解成 D-木糖和 D-葡萄糖，并对其他木葡聚糖寡糖如 XXXG（七糖，GlcXyl）和 XLLG（九糖，GlcXylGal）具有水解活性。异海藻糖是 AxyA 的首选底物，优于其他木葡聚糖寡糖。在 XXXG 的水解中，AxyA 从一个 XXXG 分子中释放出一个 D-木糖分子，生成 GXXG（六糖，GlcXyl）。AxyA 不含有用于分泌的信号肽，并且保持在细胞内。AxyA 的细胞内定位可能有助于确定作用于木葡聚糖寡糖的水解酶的顺序。
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