外来入侵植物空心莲子草几丁质酶特性研究

Characterization of chitinase of an alien invasive weed—Alternanthera philoxeroides (Mart. Griseb.)

外来入侵植物空心莲子草因其强抗逆性而迅速蔓延,成为有害杂草。拟研究其病程相关蛋白——几丁质酶酶学性质,为探讨该植物的抗逆机理和入侵机制提供理论依据。空心莲子草经乙烯利处理后,其叶片蛋白质提取液在4℃经40～60%饱和硫酸铵溶液沉淀,SephadexG-75洗脱后得几丁质酶液。结果表明:空心莲子草几丁质酶最适反应pH为5.7左右,在pH4.0～8.0均表现稳定,当pH小于4.0和大于8.0时酶活力丧失50%以上,在pH2.0和10.0时没有活力;在30℃-80℃范围内,酶均具较高活性,最适反应温度为70℃左右,温度高于80℃后,酶稳定性下降;当底物浓度小于1.25%时,酶活力随底物浓度的增加而增加,在底物浓度大于1.25%浓度时,活力增加的趋势减缓。结果提示:也许空心莲子草的强抗逆性是因为其几丁质酶具较高的温度耐受性和较大的pH作用范围。

Because of its strong resistance to environmental stresses, Alternanthera philoxeroides, an alien invasive plant, has fast become a severe weed in China. In order to explore the mechanism of its strong resistance and invasiveness, we studied the properties of its chitinase, one of the pathogenesis-related proteins in plant. The protein was extracted from the leaves treated by ethylene, precipitated with 40-60% ammonium sulfate and isolated by Sephadex G-75 chromatography. An enzymatic assay showed that the optimum pH for this enzyme was about 5.7 and it was stable in the range of 4.0 to 8.0 pH. It would loss more than 50% of its activity when pH was lower than 4.0 or higher than 8.0 and almost had no activity when pH was 2.0 or 10.0. It had high endurance to wide range of temperatures and its activity was high from 30℃to 80℃. Its optimum temperature was about 70℃ and it began to loss its activity when temperature was higher than 80℃. It was also found that the reaction velocity of this enzyme increased with the increase of its substrate concentration when the concentration was lower than 1.25%. All of these suggested that high endurance of this enzyme to temperature and acidity or alkalinity might have contributed to Alternanthera philoxeroid＇s strong resistance to environmental stresses.