A bacterial terpene synthase from Cryptosporangium arvum was characterised as a multiproduct β-himachalene synthase. In vitro studies showed not only a high promiscuity with respect to its numerous sesquiterpene products, including the structurally demanding terpenes longicyclene, longifolene and α-longipinene, but also to its substrates, as additional activity was observed with geranyl- and geranylgeranyl diphosphate. In-depth mechanistic investigations using isotopically labelled precursors regarding the stereochemical course of both 1,11-cyclisation and 1,3-hydride shift furnished a detailed catalytic model suggesting the molecular basis of the observed low product selectivity. The enzyme's synthetic potential was also exploited in the preparation of sesquiterpene isotopomers, which provided insights into their EIMS fragmentation mechanisms.

中文翻译：

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隐孢子虫多产物β-喜马林烯合酶的机理研究。

来自隐孢子虫的细菌萜烯合酶被表征为多产物β-himachalene合酶。体外研究表明，不仅其多种倍半萜烯产品（包括结构要求高的萜烯，长环戊烯和α-longipinene）具有很高的混杂性，而且其底物也是如此，因为在二磷酸香叶基和香叶基香叶基二磷酸中观察到了额外的活性。使用同位素标记的前体进行的有关1,11-环化和1,3-氢化物转变的立体化学过程的深入机理研究提供了详细的催化模型，表明观察到的低产物选择性的分子基础。该酶的合成潜能也被用于倍半萜烯异构体的制备，这为他们的EIMS片段化机理提供了见识。