An alternative mechanism of product chain-length determination in type III geranylgeranyl diphosphate synthase
An alternative mechanism of product chain-length determination in type III geranylgeranyl diphosphate synthase
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DOI：
10.1046/j.1432-1033.2003.03583.x
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发表时间：
2003-05-01
期刊：
影响因子：
--
通讯作者：
Nishino, T
中科院分区：
文献类型：
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作者：
Hemmi, H;Noike, M;Nishino, T
(ALL-E)戊二磷酸合成酶催化异戊烯基二磷酸盐与烯丙基二磷酸盐的连续缩合，产生不同链长的产物，每个酶的链长是唯一的。一些短链(ALL-E)戊二磷酸合成酶，即法尼基二磷酸合成酶和香叶基二磷酸合成酶，在烯丙基底物结合部位附近含有特征氨基酸序列，这些氨基酸序列在决定产物的链长方面发挥了作用。然而，在这些根据这些特征的拥有模式被分为几种类型的酶中，III型香叶基香叶基二磷酸合成酶缺乏这些特征，它由真核生物(植物除外)的酶组成。在这项研究中，我们报告了在保守的G(Q/E)基序之前的第二个位置的突变，该基序远离已被充分研究的区域，影响了酿酒酵母的III型香叶基香叶基二磷酸合成酶的产物的链长。这清楚地表明，一种新的机制在这种类型的酶的产物测定中起作用。我们还在此表明，古生菌中链酶的相应位置的突变也改变了其产物特异性。这些结果为(ALL-E)戊烯基二磷酸合成酶的分子进化提供了有价值的信息。
(All-E ) prenyl diphosphate synthases catalyze the consecutive condensation of isopentenyl diphosphates with allylic prenyl diphosphates, producing products with various chain-lengths that are unique for each enzyme. Some short-chain (all-E ) prenyl diphosphate synthases, i.e. farnesyl diphosphate synthases and geranylgeranyl diphosphate synthases contain characteristic amino acid sequences around the allylic substrate binding sites, which have been shown to play a role in determining the chain-length of the product. However, among these enzymes, which are classified into several types based on the possessive patterns of such characteristics, type III geranylgeranyl diphosphate synthases, which consist of enzymes from eukaryotes (excepting plants), lack these features. In this study, we report that mutagenesis at the second position before the conserved G(Q/E) motif, which is distant from the well-studied region, affects the chain-length of the product for a type III geranylgeranyl diphosphate synthase from Saccharomyces cerevisiae . This clearly suggests that a novel mechanism is operative in the product determination for this type of enzyme. We also show herein that mutagenesis at the corresponding position of an archaeal medium-chain enzyme also alters its product specificity. These results provide valuable information on the molecular evolution of (all-E ) prenyl diphosphate synthases.