The bifurcation of the cyanogenic glucoside and glucosinolate biosynthetic pathways
The bifurcation of the cyanogenic glucoside and glucosinolate biosynthetic pathways
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DOI：
10.1111/tpj.13023
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发表时间：
2015-11-01
期刊：
影响因子：
7.2
通讯作者：
Moller, Birger Lindberg
中科院分区：
文献类型：
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作者：
Clausen, Mette;Kannangara, Rubini M.;Moller, Birger Lindberg
高粱中生氰葡萄糖苷dhurrin的生物合成途径先前已被证明涉及（E）-和（Z）-对羟基苯乙醛肟的连续生产。在这项研究中，我们使用了从野生型和突变高粱或瞬时转化的本氏烟草制备的微粒体，以证明CYP 79 A1催化酪氨酸转化为（E）-对羟基苯乙醛肟，而CYP 71 E1催化（E）-对羟基苯乙醛肟转化为相应的几何Z-异构体，这是其脱水为腈（生氰葡糖苷合成的下一个中间体）所需的。芥子油苷的生物合成也是由CYP 79家族酶的作用启动的，但下一个涉及的酶属于CYP 83家族。我们证明，来自拟南芥的CYP 83 B1不能将（E）-对羟基苯乙醛肟转化为（Z）-异构体，这阻断了生氰葡糖苷合成的途径。相反，CYP 83 B1催化（E）-对羟基苯基乙醛肟转化为S-烷基-硫代羟肟酸盐，并在最终芥子油苷核心结构中保留E-肟中间体的构型。许多微生物植物病原体能够使Z-肟解毒，但不能使E-肟解毒。CYP 79衍生的E-肟在植物防御中可能发挥重要作用。
The biosynthetic pathway for the cyanogenic glucoside dhurrin in sorghum has previously been shown to involve the sequential production of (E)- and (Z)-p-hydroxyphenylacetaldoxime. In this study we used microsomes prepared from wild-type and mutant sorghum or transiently transformed Nicotiana benthamiana to demonstrate that CYP79A1 catalyzes conversion of tyrosine to (E)-p-hydroxyphenylacetaldoxime whereas CYP71E1 catalyzes conversion of (E)-p-hydroxyphenylacetaldoxime into the corresponding geometrical Z-isomer as required for its dehydration into a nitrile, the next intermediate in cyanogenic glucoside synthesis. Glucosinolate biosynthesis is also initiated by the action of a CYP79 family enzyme, but the next enzyme involved belongs to the CYP83 family. We demonstrate that CYP83B1 from Arabidopsis thaliana cannot convert the (E)-p-hydroxyphenylacetaldoxime to the (Z)-isomer, which blocks the route towards cyanogenic glucoside synthesis. Instead CYP83B1 catalyzes the conversion of the (E)-p-hydroxyphenylacetaldoxime into an S-alkyl-thiohydroximate with retention of the configuration of the E-oxime intermediate in the final glucosinolate core structure. Numerous microbial plant pathogens are able to detoxify Z-oximes but not E-oximes. The CYP79-derived E-oximes may play an important role in plant defense.