Comparison of the enzymatic properties of ent-copalyl diphosphate synthases in the biosynthesis of phytoalexins and gibberellins in rice
Comparison of the enzymatic properties of ent-copalyl diphosphate synthases in the biosynthesis of phytoalexins and gibberellins in rice
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DOI：
10.1271/bbb.70615
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发表时间：
2008-02-01
影响因子：
1.6
通讯作者：
Dairi, Tohru
中科院分区：
文献类型：
--
作者：
Hayashi, Yutaka;Toyomasu, Tomonobu;Dairi, Tohru
水稻基因组包含两个前-共alyl二磷酸合成酶基因：OsCPS1参与赤霉素（植物激素）的生物合成，OsCPS2/OsCyc2参与水稻抗毒素A-F和植物cassanes A-E（植物抗毒素）的合成。我们对重组OsCPS2/OsCyc2在n端与标签蛋白融合的酶学特性进行了表征，并将其与OsCPS1进行了比较。OsCPS2/OsCyc2的几个酶学性质，包括最适pH、最适温度、二价阳离子需求和对二磷酸香叶基（GGDP）底物的动力学值，与OsCPS1几乎相同。而OsCPS2/OsCyc2活性未被50-60 μ m GGDP底物抑制，而OsCPS1活性被GGDP底物抑制。此外，100 μ m Amo-1618（一种赤霉素生物合成抑制剂）对OsCPS1活性的抑制作用约为70%，而对OsCPS2/OsCyc2活性的抑制作用约为10%。这些结果表明，尽管OsCPS2/OsCyc2催化的反应步骤与OsCPS1相同，但OsCPS2/OsCyc2的性质与OsCPS1有部分不同。
The rice genome contains two ent-copalyl diphosphate synthase genes: OsCPS1 acts in gibberellin (phytohormone) biosynthesis, and OsCPS2/OsCyc2 acts in the synthesis of oryzalexins A-F and phytocassanes A-E (phytoalexins). We characterized the enzymatic properties of recombinant OsCPS2/OsCyc2 fused with a tag-protein at the N-terminus, and compared them to those of OsCPS1. Several enzymatic properties of OsCPS2/OsCyc2, including the optimal pH, optimal temperature, divalent cation requirement, and kinetic values for the geranylgeranyl diphosphate (GGDP) substrate, were almost the same as those of OsCPS1. However, OsCPS2/OsCyc2 activity was not inhibited by 50-60 mu m GGDP substrate, by which the OsCPS1 activity was inhibited. Furthermore, the OsCPS1 activity exhibited approximately 70% inhibition by 100 mu m Amo-1618 (a gibberellin biosynthetic inhibitor), whereas the OsCPS2/OsCyc2 activity exhibited approximately 10% inhibition. These results indicate that the properties of OsCPS2/OsCyc2 were partially different from those of OsCPS1, although OsCPS2/OsCyc2 catalyzes the same reaction step as OsCPS1.