植物螯合物之合成及分析研究

Abstract

近幾年研究報告指出，植物體在受到過量重金屬的刺激時，會產生一種功能相似於動物體之Metallothioenin的勝?，稱為植物螯合物(Phytochelatin)。此勝?從低等藻類到高等植物中皆能發現，具有重金屬的去毒及調節功能。在1990年有文獻指出，它亦具有半導體( semi－conductance ）的性質。 植物螯合物具有特殊的結構( r - Glu - Cys ) n - Gly ，其合成是不經由核醣體而產生，故無法利用分子遺傳技術來大量合成。本文嘗試利用有機合成及酵素催化反應來合成，並探討其與重金屬間的關係。 在此所使用的有機合成方法是固相勝?合成法，分成兩方面來合成：第一種為人工合成，第二種則利用自動勝?合成儀來合成植物螯合物。另外，還嘗試利用食品級用之酵素－alcalase來催化合成。最後將已合成出的植物螯合物( n=7)與鎘離子進行反應並測試其關係。

Toxic metal ions are thought to enter the cell by means of the same uptake systems that move such physiologically important ions as Cu and Zn. In plants, excess intracellular heavy metals induce biosynthesis of peptide called Phytochelatin. In contrast to animal systems, plants possess nonprotein metal-binding polypeptides that, although differing in structure and biosynthesis, may be functionally analogous to metallothioneins--detoxification and homeostasis of heavy metal. Phytochelatins possess special structures--(γ-Glu-Cys)n-Gly. The γ-glutamyl linkage presents in these peptides imply that they are not synthesized via mRNA. So phytochelatin can’t be synthesized by molecular genetic techiques. The gists of the thesis are to describe how to synthesize phytochelatin by the combination of organic and enzymic synthesis and to research what relationship between heavy metal ion and phytochelatin.