Chemistry on Peptides Induced in Plants Treated with Cadmium Ion

在镉离子处理的裂变酵母中发现了cadytin。它们的结构特点是含有γ -谷氨酰半胱氨酸片段，并已通过微化学反应和酶反应测定。在本研究中，建立了两种特异性分析cadytin的方法。其中之一是高效液相色谱法（HPLC）分析cadyins的荧光DACM衍生物。另一种是高效液相色谱法分析它们的4-乙烯基吡啶衍生物，在255 nm处具有特定的紫外吸光度。虽然后者的灵敏度不如前者，但后者的方法适合于分析cadystins的分子种类，因为衍生物形成反应提供了与各自cadystins对应的单一产物，并且衍生物在分析过程中足够稳定。前一种方法比后一种方法灵敏度高，适用于痕量cadytin的检测。采用前一种方法测定了Cd^<++>处理水稻根系诱导的cadysti…More ns。结果表明，在未处理的根中，谷胱甘肽（GSH）是主要的谷胱甘肽，Cd^<++>处理下，新诱导的cadystins伴随着谷胱甘肽的急剧下降。接下来，研究了cadytin的酶合成。在结构分析中发现的羧基肽酶（CPase）的一个有趣的特异性被用于这一目的。这就是CPase不切割γ - glu - cys键而是切割Cys-Gly和Cys-Glu键的特异性。在高底物浓度条件下，用CPase Y处理谷胱甘肽。酶反应产生了6种主要产物。其中2例为cadystin (γ - EC)_2G和（γ - EC）_3G。其他产物为（γ EC）、（γ EC）_2、（γ EC）_3和（γ EC）_2的脱水产物。结果表明，在高底物浓度条件下，GSH主要通过CPase Y代谢途径，并建立了一种单步合成cadyins的方法。少

Cadystins had been found in a fission yeast treated with cadmium ion. Their structures are characteristic to contain gamma-glutamyl-cysteine moiety and had been determined by means of micro-chemical reactions and enzymic reactions.During the present research, two methods to analyze cadystins specifically were established. One of them is HPLC analysis of fluorescent DACM derivatives of cadystins. The other one is HPLC analysis of their 4-vinylpyridine derivatives bearing specific UV absorbance at 255 nm. Although the sensitivity of the latter is not better than the former, the latter method was suitable to analyze the molecular species of cadystins because the derivate formation reaction afforded a single product corresponding to the respective cadystins and because the derivatives are stable enough during the analysis. The former method is suitable to detect trace amount of cadystins,because it is more highly sensitive than the latter. The former method was applied to determine cadysti … More ns induced in the root of rice plant treated with Cd^<++>. The results suggested that glutathione (GSH) is the major SH peptide in non-treated root, and that cadystins were newly induced accompanied by dramatic decrease of GSH, by treatment with Cd^<++>.Next, the enzymic synthesis of cadystins was examined. An interesting specificity of carboxypeptidase (CPase) found in the structure analysis was applied for this purpose. That is the specificity that CPase does not cleave gamma-Glu-Cys bond and that it cleaves Cys-Gly and Cys-Glu linkage. GSH was treated with CPase Y under a high substrate concentration condition. The enzymic reaction afforded major 6 products. Two of them were cadystin (gamma EC)_2G and (gamma EC)_3G. The other products were (gamma EC), (gamma EC)_2, (gamma EC)_3, and dehydrate product of (gamma EC)_2. The results suggested the major metabolic pathway of GSH by CPase Y under high substrate concentration condition and a method to synthesize cadystins in a simgle step was established. Less