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Title: | 植物螯合物合成酵素的部分分離與特性鑑定 Partial Purification and Characterization of Phytochelatin Synthase |
Authors: | 顏世隆 |
Publication Year : | 1993 |
Degree: | 碩士 |
Abstract: | 植物遭遇重金屬逆境時在生理上會發生一些變化以抵抗逆境。經銅處理後,調查與抗性有關的酵素發現,超氧化歧化酵素的同功酵素幾無變化但其mRNA有明顯增加。過氧化酵素的同功酵素則隨處理時間長短而異。另外在重金屬處理下,植物體內的含氫硫基物質會大量增加,如glutathione和植物螯合物(phytochelatins)。植物螯合物雖是由胺基酸所組成的多勝?,但非由核醣體合成,而是由酵素所合成。本實驗以水稻幼苗為植物材料,由QAE A-50離子交換管柱層析、PBE94等電焦集管柱層析、AcA 44膠體過濾管柱層析來純化植物螯合物合成酵素。此酵素的等電點大約是4.0左右,分子量則大約是100 kDa,此酵素在37℃時有最佳的催化能力,而其最適酸鹼值則是在7.5左右。二價重金屬離子對此酵素有啟動的作用,但是鈣離子和鎂離子並不具有啟動植物螯合物合成酵素的能力,另外一價的銀離子亦具有啟動植物螯合物合成酵素催化的能力。 Rice plants treated with 50 μM copper ion showed the changes in the isozyme pattern of peroxidase. Though the mRNA of superoxide dismutase (SOD) accumulated in copper-treated rice seedlings, however, the isozymes of SOD had no change. Meanwhile, the synthesis of phytochelatins, heavy metal binding polypeptides, were induced. Phytochelatins is not a gene product through regular protein sythesis, but a biosythetic production of a series of enzymes, including phytochelatin synthase. Phytochelatin synthase was extracted from 2-3 week-old rice seedlings and islated through a series purification steps including acetone precipitation, QAE A-50 anion exchange chromatography, PBE94 chromatofocusing chromatography and AcA 44 gel filtration chromatography. The isoelectric point of phytochelatin synthase is around 4.0 and its molecular weight is about 100 kDa. The temperature and pH optima of this enzyme are 37℃ and pH 7.5, respectively. Cadmium, lead, nickel, manganese and copper ions effectviely stimulate this enzyme, but Ca2+ and Mg2+ do not. Heavy metals, such as silver ion and MoO42- also enhance the activity of phytochelatin synthase. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75966 |
Fulltext Rights: | 未授權 |
Appears in Collections: | 植物科學研究所 |
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