Department of Biochemistry, Biophysics, & Molecular Biology, Iowa State University, Ames, IA 50011, USA.
Nat Prod Rep. 2010 Nov;27(11):1521-30. doi: 10.1039/c0np00019a. Epub 2010 Oct 1.
In his original exposition of the biogenetic isoprenoid rule, L. Ruzicka noted the structural identity between the fused A/B rings of triterpenoids/sterols and certain multicyclic diterpenoids as part of the impetus leading to that profound insight. His prescient hypothesis that this chemical structure relationship reflects similarities in the initial cyclization of these diterpenoids with that occurring in triterpenoid biosynthesis has since been verified. However, this chemical structure relationship does not continue to hold true for the additional rings found in many of these di- and tri- terpenoid natural products. This is now appreciated to arise from differences in their subsequent biogenesis, specifically further cyclization and/or rearrangement of these diterpenoids after formation of an initial bicyclic intermediate in a separately catalyzed reaction. The trivial name for the hydrocarbon skeleton of the most commonly found version of the corresponding unique intermediate forms the basis for a unifying “” designation. This defines a large super-family of diterpenoids that contains nearly 7,000 already known natural products. Many of these are found in plants, where the requisite biosynthetic machinery for gibberellin phytohormones, particularly the relevant diterpene cyclases, provides a biosynthetic reservoir that appears to have been repeatedly drawn upon to evolve new labdane-related diterpenoids. The potent biological activity of the “ancestral” gibberellins, which has led to the independent evolution of distinct gibberellin biosynthetic pathways in plants, fungi, and bacteria, is further discussed as an archetypical example of the selective pressure driving the observed diversification of the large super-family of labdane-related diterpenoid natural products.
在他对生源异戊二烯规则的最初阐述中，L. Ruzicka 注意到三萜类/固醇的 A/B 稠合双环和某些多环二萜类化合物之间的结构同一性，这是导致这一深刻见解的部分动力。他有先见之明的假设是，这种化学结构关系反映了这些二萜类化合物与三萜类生物合成中初始环化的相似性，此后这一假设得到了验证。然而，对于许多此类二萜和三萜天然产物中发现的额外环，这种化学结构关系不再成立。现在人们认识到，这是由于它们随后的生物发生存在差异，特别是在形成初始双环中间体后，这些二萜类化合物会进一步环化和/或重排。相应独特中间体的最常见版本的烃骨架的俗名构成了统一“”命名的基础。这定义了一个庞大的二萜超家族，其中包含近 7000 种已被发现的天然产物。其中许多存在于植物中，植物中存在赤霉素植物激素所必需的生物合成机制，特别是相关的二萜环化酶，为进化出新的 labdane 相关二萜类化合物提供了生物合成库，似乎已经反复利用这个库来进化出新的 labdane 相关二萜类化合物。“原始”赤霉素具有强烈的生物学活性，导致植物、真菌和细菌中独立进化出不同的赤霉素生物合成途径，这进一步讨论了作为驱动观察到的 labdane 相关二萜类天然产物的大型超家族多样化的选择压力的典型范例。
