Biosynthesis of rice phytoalexin:: Enzymatic conversion of 3β-hydroxy-9β-pimara-7,15-dien-19,6β-olide to momilactone A
Biosynthesis of rice phytoalexin:: Enzymatic conversion of 3β-hydroxy-9β-pimara-7,15-dien-19,6β-olide to momilactone A
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DOI：
10.1271/bbb.66.566
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发表时间：
2002-03-01
影响因子：
1.6
通讯作者：
Kodama, O
中科院分区：
文献类型：
--
作者：
Atawong, A;Hasegawa, M;Kodama, O
在水稻叶片中3 β-羟基-9 β-海葵-7，15-二烯-19，6 β-二烯的3-位上脱氢可合成一种主要的水稻二萜植物抗毒素-龟鳖内酯A。通过对天然和合成化合物进行GC/MS分析后比较质谱和保留时间，证实了紫外线照射水稻叶片中3 β-羟基-9 β-庚二烯-7，15-二烯-19，6 β-庚二烯的存在。来自UV照射的水稻叶片的可溶性蛋白质级分显示出脱氢酶活性，将3 β-羟基-9 β-庚二烯-7，15-二烯-19，6 β-庚二烯转化为momilactone A。该酶需要NAD（+）或NADP（+）作为氢受体。反应的最适pH为8。当NAD（+）作为辅因子以1 mM浓度提供时，对3 β-羟基-9 β-匹马拉-7，15-二烯-19，6 β-脱氢酶的Km值为36 μ m.3 β-羟基-9 β-匹马拉-7，15-二烯-19，6 β-脱氢酶及其脱氢酶活性通过UV照射以时间依赖性方式诱导。
Momilactone A, a major rice diterpene phytoalexin, could be synthesized by dehydrogenation at the 3-position of 3beta-hydroxy-9beta-pimara-7,15-dien-19,6beta-olide in rice leaves. The presence of 3beta-hydroxy-9beta-pimara-7,15-dien-19,6beta-olide in UV-irradiated rice leaves was confirmed by comparing the mass spectra and retention times after a GC/MS analysis of the natural and synthetic compounds. The soluble protein fraction from UV-irradiated rice leaves showed dehydrogenase activity to convert 3beta-hydroxy-9beta-pimara-7,15-dien-19,6betaolide into momilactone A. The enzyme required NAD(+) or NADP(+) as a hydrogen acceptor. The optimum pH for the reaction was 8. The K-m value to 3beta-hydroxy-9beta-pimara-7,15-dien-19,6beta-olide was 36 mum when NAD(+) was supplied as a cofactor at a concentration of 1 mm. 3beta-Hydroxy-9beta-pimara-7,15-dien-19,6beta-olide and its dehydrogenase activity were induced in a time-dependent manner by UV irradiation.