Geosmin biosynthesis.: Streptomyces coelicolor germacradienol/germacrene D synthase converts farnesyl diphosphate to geosmin
Geosmin biosynthesis.: Streptomyces coelicolor germacradienol/germacrene D synthase converts farnesyl diphosphate to geosmin
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DOI：
10.1021/ja062669x
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发表时间：
2006-06-28
影响因子：
15
通讯作者：
Cane, David E.
中科院分区：
文献类型：
--
作者：
Jiang, Jiaoyang;He, Xiaofei;Cane, David E.
土臭素是潮湿土壤特有气味的来源。孵育由SCO 6073编码的重组吉马放射烯醇合酶革兰氏阳性土壤细菌天蓝色链霉菌（Streptomyces coelicolor）的（SC9B1.20）基因与法呢基二磷酸（2，FPP）在Mg 2+存在下产生（4S，7 R）-大根香叶-1（10）E，5E-二烯-11-醇（3）（74%），（-）-（7S）-大根香叶烯D（4）（10%），土臭素（1）（13%）和一种碳氢化合物，初步确定其结构为octalin 5（3%）。重组大根香叶烯醇合酶与[1，1 - 2 H 2]FPP（2a）、（1 R）-[1- 2 H]-FPP（2b）和（1 S）-[1- 2 H]-FPP（2c）以及与FPP（2）在D2 O中的单独孵育，和GC-MS分析所产生的氘代产物支持土臭素形成的机制，涉及质子引发的环化和逆-Prins将最初形成的大根香叶二烯醇断裂，得到中间体5，然后进行5的质子化，1，2-氢化物移位，并捕获水。
Geosmin is responsible for the characteristic odor of moist soil. Incubation of recombinant germacradienol synthase, encoded by the SCO6073 (SC9B1.20) gene of the Gram-positive soil bacteriumStreptomyces coelicolor, with farnesyl diphosphate (2, FPP) in the presence of Mg2+gave a mixture of (4S,7R)-germacra-1(10)E,5E-diene-11-ol (3) (74%), (−)-(7S)-germacrene D (4) (10%), geosmin (1) (13%), and a hydrocarbon, tentatively assigned the structure of octalin5(3%). Individual incubations of recombinant germacradienol synthase with [1,1-2H2]FPP (2a), (1R)-[1-2H]-FPP (2b), and (1S)-[1-2H]-FPP (2c), as well as with FPP (2) in D2O, and GC−MS analysis of the resulting deuterated products supported a mechanism of geosmin formation involving proton-initiated cyclization and retro-Prins fragmentation of the initially formed germacradienol to give intermediate5, followed by protonation of5, 1,2-hydride shift, and capture of water.