Mg-dechelation activity in radish cotyledons with artificial and native substrates, Mg-chlorophyllin a and chlorophyllide a.
Mg-dechelation activity in radish cotyledons with artificial and native substrates, Mg-chlorophyllin a and chlorophyllide a.
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DOI：
10.1016/j.plaphy.2005.03.009
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发表时间：
2005-05
期刊：
影响因子：
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通讯作者：
Toshiyuki Suzuki;Tadashi Kunieda;Fumiko Murai;S. Morioka;Y. Shioi
中科院分区：
文献类型：
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作者：
Toshiyuki Suzuki;Tadashi Kunieda;Fumiko Murai;S. Morioka;Y. Shioi
采用人工底物mg -叶绿素a （Chlin）和天然底物叶绿素a （Chlide）对萝卜子叶提取物中mg -脱酸活性进行了研究。除了已知的一种小分子量金属螯合物质（MCS）外，当氯作为底物时，还存在释镁蛋白（MRP）。然而，只有MCS与天然底物具有mg脱羧活性。为了检验MRP解离成蛋白质片段和具有MCS活性的小分子质量化合物的可能性，进行了低离子强度和高离子强度缓冲液的提取。然而，没有证据表明MCS是MRP的一部分。抑制剂研究表明，MCS和MRP对抑制剂具有不同的敏感性，特别是对螯合剂铁和EDTA，当以Chlin为底物时。铁对MRP没有影响，但严重降低了两种底物的MCS活性。在衰老过程中，MRP活性增加，表明MRP受到诱导，而MCS活性基本不变。这些结果表明不同化合物的反应机制不同。这些发现表明，MRP和MCS是独立存在的，MCS被认为是一种在Chl分解途径中催化Mg-dechelation反应的物质，尽管MCS在衰老过程中没有被诱导。讨论了MRP和MCS与草莓果实小分子质量物质的关系。
The Mg-dechelation activity in extracts from radish (Raphanus sativus L.) cotyledons was investigated using an artificial substrate, Mg-chlorophyllin a (Chlin) and the native substrate, chlorophyllide a (Chlide). In addition to a known a small molecular weight metal-chelating substance (MCS), Mg-releasing protein (MRP) was present when Chlin was used as the substrate. However, only MCS had Mg-dechelation activity with the native substrate. To examine the possibility of the dissociation of MRP into a protein moiety and a small molecular mass compound with an activity like MCS, extraction with low and high ionic strength buffers was carried out. No evidence was obtained that MCS is a moiety of MRP, however. Inhibitor studies showed that MCS and MRP had different susceptibilities to the inhibitors, especially to the chelators tiron and EDTA when Chlin was used as the substrate. Tiron had no effect on MRP, but it severely reduced MCS activity in both substrates. The activity of MRP increased during senescence, indicating the induction of MRP, while the activity of MCS was almost unchanged. These results suggest different reaction mechanisms by independent compounds. These findings suggest that MRP and MCS are present independently, and MCS is postulated to be a substance that catalyzes the Mg-dechelation reaction in the breakdown pathway of Chl, although MCS was not induced during senescence. The properties of MRP and MCS in relation to the small molecular mass substance obtained from strawberry fruit are also discussed.