Kaku Tomomi, Tabuchi Akira, Wakabayashi Kazuyuki, Hoson Takayuki
Department of Biological Sciences, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, 558-8585 Japan.
Plant Cell Physiol. 2004 Jan;45(1):77-82. doi: 10.1093/pcp/pch007.
Addition of xyloglucan-derived oligosaccharides shifted the wall-bound xyloglucans to a lower molecular mass distribution and increased the cell wall extensibility of the native epidermal tissue strips isolated from azuki bean (Vigna angularis) epicotyls. To ascertain the mechanism of oligosaccharide function, we examined the action of a xyloglucan endotransglucosylase/hydrolase (XTH) showing both endotransglucosylase and endohydrolase activities, isolated from azuki bean epicotyl cell walls, in the presence of xyloglucan oligosaccharides. The addition of xyloglucan oligosaccharides enhanced the xyloglucan-degrading activity of XTH against isolated xyloglucan substrates. When the methanol-fixed epidermal tissue strips were incubated with XTH, the molecular mass of wall-bound xyloglucans was decreased and the cell wall extensibility increased markedly in the presence of the oligosaccharides. These results suggest that xyloglucan oligosaccharides stimulate the degradation of xyloglucans by enhancing the XTH activity within the cell wall architecture, thereby increasing the cell wall extensibility in azuki bean epicotyls.
添加木葡聚糖衍生的寡糖可使细胞壁结合的木葡聚糖向较低分子量分布转变，并增加从赤豆（Vigna angularis）上胚轴分离的天然表皮组织条的细胞壁伸展性。为了确定寡糖功能的机制，我们研究了一种从赤豆上胚轴细胞壁中分离出的具有转葡糖基酶和水解酶活性的木葡聚糖内转糖基酶/水解酶（XTH）在木葡聚糖寡糖存在下的作用。木葡聚糖寡糖的添加增强了XTH对分离的木葡聚糖底物的木葡聚糖降解活性。当用XTH孵育甲醇固定的表皮组织条时，在寡糖存在下，细胞壁结合的木葡聚糖分子量降低，细胞壁伸展性显著增加。这些结果表明，木葡聚糖寡糖通过增强细胞壁结构内的XTH活性来刺激木葡聚糖的降解，从而增加赤豆上胚轴的细胞壁伸展性。
