Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan, ROC.
Biochem Biophys Res Commun. 2010 Oct 1;400(4):758-62. doi: 10.1016/j.bbrc.2010.09.001. Epub 2010 Sep 7.
Undecaprenyl pyrophosphate synthase (UPPS) is a cis-type prenyltransferases which catalyzes condensation reactions of farnesyl diphosphate (FPP) with eight isopentenyl pyrophosphate (IPP) units to generate C(55) product. In this study, we used two analogues of FPP, 2-fluoro-FPP and [1,1-(2)H(2)]FPP, to probe the reaction mechanism of Escherichia coli UPPS. The reaction rate of 2-fluoro-FPP with IPP under single-turnover condition is similar to that of FPP, consistent with the mechanism without forming a farnesyl carbocation intermediate. Moreover, the deuterium secondary KIE of 0.985±0.022 measured for UPPS reaction using [1,1-(2)H(2)]FPP supports the associative transition state. Unlike the sequential mechanism used by trans-prenyltransferases, our data demonstrate E. coli UPPS utilizes the concerted mechanism.
十一碳烯焦磷酸合酶（UPPS）是一种顺式型 prenyltransferase，可催化法呢基二磷酸（FPP）与 8 个异戊烯焦磷酸（IPP）单元的缩合反应，生成 C(55)产物。在这项研究中，我们使用两种 FPP 的类似物，2-氟-FPP 和 [1,1-(2)H(2)]FPP，来探究大肠杆菌 UPPS 的反应机制。在单轮条件下，IPP 与 2-氟-FPP 的反应速率与 FPP 相似，这与不形成法呢基碳正离子中间体的机制一致。此外，使用 [1,1-(2)H(2)]FPP 测量的 UPPS 反应的氘次级 KIE 为 0.985±0.022，支持缔合过渡态。与反式 prenyltransferase 采用的顺序机制不同，我们的数据表明大肠杆菌 UPPS 采用了协同机制。
