Identification and characterization of α-xylosidase involved in xyloglucan degradation in Aspergillus oryzae
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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, Glc4Xyl3) and XLLG (nonasaccharide, Glc4Xyl3Gal2). 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, Glc4Xyl2). 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.
Keywordsα-xylosidase Aspergillus oryzae Xyloglucan Glycoside hydrolase family 31
We thank the National Research Institute of Brewing (Hiroshima, Japan) for the A. oryzae RIB40 strain.
This study was supported by the Japan Society for the Promotion of Science KAKENHI (Grant-in-Aid for Scientific Research B, Grant No. 18H02132).
Compliance with ethical standards
This article does not contain any studies with human participants or animals performed by any of the authors.
Conflict of interest
The authors declare that they have no conflicts of interest.
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