Substrate specificities of tobacco chitinases
Substrate specificities of tobacco chitinases
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DOI：
10.1046/j.1365-313x.1998.00116.x
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发表时间：
1998-04-01
期刊：
影响因子：
7.2
通讯作者：
Legrand, M
中科院分区：
文献类型：
--
作者：
Brunner, F;Stintzi, A;Legrand, M
从对烟草花叶病毒过敏的烟叶中纯化出10个几丁质酶（1,4- n -乙酰- β - d -氨基葡萄糖聚糖水解酶，EC 3.2.1.14）。这10种酶分别属于5种不同结构的植物几丁质酶，它们与几种潜在底物如几丁质、β -1,4 n -乙酰- d -氨基葡萄糖（GlcNAc）聚合物、壳聚糖（部分去乙酰化的几丁质）、可变长度的几丁质低聚物和细菌细胞壁等一起培养。烟草几丁质酶都是能从几丁质中释放低聚物并能以不同速率进一步加工几丁质低聚物的内源性酶。用高效液相色谱法对几丁质反应产物进行了分离和定量，并观察了不同种类几丁质酶对寡聚物积累和降解的差异动力学。取决于要水解的底物，每个异构体显示出不同的活性谱。例如，I类基型在几丁质和（GlcNAc）上最活跃（4-6），而III类基型在诱导细菌裂解方面最有效。V类和VI类几丁质酶比几丁质聚合物本身更容易水解几丁质低聚物。总之，这些数据表明，这10种烟草几丁质酶是互补酶，可能对其底物有协同作用。本文讨论了它们在植物通过攻击病原体的结构成分进行防御和通过成熟信号分子进行植物发育中的意义。
Ten tobacco chitinases (1,4-N-acetyl-beta-D-glucosaminide glycanhydrolase, EC 3.2.1.14) were purified from tobacco leaves hypersensitively reacting to tobacco mosaic virus. The 10 enzymes, which belong to five distinct structural classes of plant chitinases, were incubated with several potential substrates such as chitin, a beta-1,4 N-acetyl-D-glucosamine (GlcNAc) polymer, chitosan (partially deacetylated chitin), chitin oligomers of variable length and bacterial cell wall. Tobacco chitinases are all endotype enzymes that liberate oligomers from chitin and are capable of processing the chito-oligomers further at differential rates. Chitin reaction products were separated and quantified by HPLC and differential kinetics of oligomer accumulation and degradation were observed with the distinct classes of chitinases. Depending on the substrate to be hydrolysed, each isoform displayed a different spectrum of activity. For example, class I isoforms were the most active on chitin and (GlcNAc)(4-6) whereas class III basic isoforms were the most efficient in inducing bacterial lysis. Class V and class VI chitinases were shown to more readily hydrolyse chitin oligomers than the chitin polymer itself. Together, these data indicate that the 10 tobacco chitinases represent complementary enzymes which may have synergistic effects on their substrates. This paper discusses their implication in plant defense by attacking pathogen's structural components and in plant development by maturing signal molecules.