The enzymatic activity of fungal xylanase is not necessary for its elicitor activity
The enzymatic activity of fungal xylanase is not necessary for its elicitor activity
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DOI：
10.1104/pp.121.2.391
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发表时间：
1999-10-01
期刊：
影响因子：
7.4
通讯作者：
Boller, T
中科院分区：
文献类型：
--
作者：
Enkerli, J;Felix, G;Boller, T
木霉的木聚糖酶是多种植物防御反应的有效激发子。为了确定引发子活性是否需要酶活性，我们使用定点诱变来降低里氏木霉木聚糖酶II的催化活性。为此，位于210位的谷氨酸残基（该酶家族活性中心的一部分）被改变为天冬氨酸（E210D）或丝氨酸（E210S）。野生型和突变型木聚糖酶II在酵母细胞中表达并纯化到均匀性。与野生型木聚糖酶相比，E210D的酶活性降低了100倍，E210S的酶活性降低了1000倍。相比之下，这些突变形式的激发子活性没有相应的下降。他们充分刺激悬浮培养番茄（Lycopersicon esculentum）细胞的培养基碱化和乙烯生物合成，以及番茄和烟草植株叶片的过敏性坏死。这些结果为真菌木聚糖酶的激发子活性不是酶活性所必需的直接证据。
Fungal xylanases from Trichoderma spp. are potent elicitors of defense responses in various plants. To determine whether enzymatic activity is necessary for elicitor activity, we used site-directed mutagenesis to reduce the catalytic activity of xylanase II from Trichoderma reesei. For this, the glutamic acid residue at position 210, which is part of the active center in this family of enzymes, was changed to either aspartic acid (E210D) or serine (E210S). Wildtype and mutated forms of xylanase II were expressed in yeast cells and purified to homogeneity. Compared with the wild-type form of xylanase II, E210D had >100-fold and E210S 1,000-fold lower enzymatic activity. In contrast, these mutated forms showed no comparable drop in elicitor activity. They fully stimulated medium alkalinization and ethylene biosynthesis in suspension-cultured tomato (Lycopersicon esculentum) cells, as well as hypersensitive necrosis in leaves of tomato and tobacco (Nicotiana tabacum) plants. These results provide direct evidence that enzyme activity is not necessary for elicitor activity of fungal xylanase.