ISOTOPICALLY SENSITIVE BRANCHING IN THE FORMATION OF CYCLIC MONOTERPENES - PROOF THAT (-)-ALPHA-PINENE AND (-)-BETA-PINENE ARE SYNTHESIZED BY THE SAME MONOTERPENE CYCLASE VIA DEPROTONATION OF A COMMON INTERMEDIATE
ISOTOPICALLY SENSITIVE BRANCHING IN THE FORMATION OF CYCLIC MONOTERPENES - PROOF THAT (-)-ALPHA-PINENE AND (-)-BETA-PINENE ARE SYNTHESIZED BY THE SAME MONOTERPENE CYCLASE VIA DEPROTONATION OF A COMMON INTERMEDIATE
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DOI：
10.1021/bi00391a025
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发表时间：
1987-08-25
期刊：
影响因子：
2.9
通讯作者：
HA, HJ
中科院分区：
文献类型：
--
作者：
CROTEAU, RB;WHEELER, CJ;HA, HJ
为了确定双环单萜烯烃（-）-α-蒎烯和（-）-β-通过碳阳离子中间体的交替去质子化，从相同的单萜环化酶生物合成产生蒎烯，比较了由无环前体[10- 2 H3，1- 3 H]香叶基焦磷酸盐产生的产物分布和由[1- 3 H]香叶基焦磷酸盐与鼠尾草的（-）-蒎烯环化酶温育产生的产物分布。改变是由部分纯化的蒎烯环化酶产生的烯烃产物的比例，该部分纯化的蒎烯环化酶产生于（-）-β-环化酶的形成的抑制。- 通过初级氘同位素效应与形成（-）-α-蒎烯（C10去质子化）的补偿刺激作用蒎烯（C4去质子化）。（-）-蒎烯环化酶以及（+）-蒎烯环化酶也表现出从氘化底物产生的无环烯烃月桂烯的比例降低，伴随着对环化产物的承诺的相应增加。同位素敏感性分支的观察，结合次级氘同位素对（+）-和（-）-蒎烯环化酶以及来自相同组织的两种其它单萜环化酶的产物形成的总速率的影响的量值的定量，支持（-）-α-环化酶的生物合成起源。蒎烯和（-）-β-通过共同的酶中间体的交替去质子化来制备蒎烯。与这些结果相一致的生物成因计划，并提出替代的建议的起源的松烯。
To determine whether the bicyclic monoterpene olefins (-)-.alpha.-pinene and (-)-.beta.-pinene arise biosynthetically from the same monoterpene cyclase by alternate deprotonations of a common carbocationic intermediate, the product distributions arising from the acyclic precursor [10-2H3,1-3H]geranyl pyrophosphate were compared with those resulting from incubation of [1-3H]geranyl pyrophosphate with (-)-pinene cyclase from Salvia officinalis. Alteration is proportions of the olefinic products generated by the partially purified pinene cyclase resulted from the suppression of the formation of (-)-.beta.-pinene (C10 deprotonation) by a primary deuterium isotope effect with a compensating stimulation of the formation of (-)-.alpha.-pinene (C4 deprotonation). (-)-Pinene cyclase as well as (+)-pinene cyclase also exhibited a decrease in the proportion of the acyclic olefin myrcene generated from the deuteriated substrate, accompanied by a corresponding increase in the commitment to cyclized products. The observation of isotopically sensitive branching, in conjunction with quantitation of the magnitude of the secondary deuterium isotope effect on the overall rate of product formation by the (+)- and (-)-pinene cyclases as well as two other monoterpene cyclases from the same tissue, supports the biosynthetic origin of (-)-.alpha.-pinene and (-)-.beta.-pinene by alternative deprotonations of a common enzymatic intermediate. A biogenetic scheme consistent with these results is presented, and alternate proposals for the origin of the pinenes are addressed.