Structure and function of arabinogalactan-proteins in cell walls of higher plants

植物细胞壁主要由纤维素和其他多糖组成，如果胶和半纤维素，以及阿拉伯半乳糖蛋白(AGPs)，这是一个蛋白多糖/糖蛋白家族。在这项研究中，我们的实验室致力于探索一种新的半乳糖苷酶，它能在不同的微生物来源中降解AGPs的碳水化合物部分。我们从冬菇中发现了一种内切β-1，3-半乳糖苷酶，并证明该酶对阐明AGPs的结构非常有用。应用几种不同类型的AGP降解酶，提出了拟南芥叶片AGP碳水化合物部分的模型结构。类似的方法允许测定萝卜根AGP的结构。我们还发现，酶降解的AGP片段具有生理功能(激发子活性)，当给药到大豆子叶上时，产生抗菌物质。

Plant cell walls consist mainly of cellulose and other polysaccharides, such as pectins and hemicelluloses as well as arabinogalactan-proteins (AGPs), a family of proteoglycans/glycoproteins. In this study, our laboratory has focused to explore a new galactanase hydrolyzing the carbohydrate moieties of AGPs in various microbial sources. We found an endo-beta-1,3-galactanase from winter mushroom and demonstrated that the enzyme is highly useful to elucidate the structure of AGPs. A model structure of the carbohydrate moieties of Arabidopsis leaf AGP has been proposed by application of several different kinds of AGP-degrading enzymes. Similar approach allowed to determine the structure of radish root AGP. We also appeared that the enzymatically degraded AGP fragments possess physiological function (elicitor activity) producing antimicrobial substances when administered to soybean cotyledons.