Biosynthesis of Squalene from Farnesyl Diphosphate in Bacteria: Three Steps Catalyzed by Three Enzymes.
Biosynthesis of Squalene from Farnesyl Diphosphate in Bacteria: Three Steps Catalyzed by Three Enzymes.
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DOI：
10.1021/acscentsci.5b00115
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发表时间：
2015
影响因子：
18.2
通讯作者：
Poulter CD
中科院分区：
文献类型：
--
作者：
Pan JJ;Solbiati JO;Ramamoorthy G;Hillerich BS;Seidel RD;Cronan JE;Almo SC;Poulter CD
角鲨烯（SQ）是真核生物和一些细菌中甾醇生物合成的中间体，也是细菌中类藿烷生物合成的中间体，它们促进宿主细胞膜稳定性和脂筏的形成。类藿烷生物合成的基因通常位于由四个高度保守的基因hpnC，hpnD，hpnE和hpnF组成的簇上，用于将法呢基二磷酸（FPP）转化为藿烯或相关的五环代谢物。虽然已知hpnF编码角鲨烯环化酶，但hpnC、hpnD和hpnE的功能尚未严格确定。将来自运动发酵单胞菌和沼泽红球藻的hpnC、hpnD和hpnE基因克隆到大肠杆菌（Escherichia coli）中，所述大肠杆菌是一种不含有与hpnC、hpnD和hpnE同源的基因的细菌，并且在体外和体内建立了它们的功能。HpnD催化两分子FPP形成前角鲨烯二磷酸（PSPP）; HpnC将PSPP转化为羟基角鲨烯（HSQ）; HpnE是胺氧化还原酶家族的成员，将HSQ还原为SQ。这三种酶催化的反应共同构成了细菌中SQ生物合成的新途径。在确定细菌hopanoid基因簇中三个高度保守基因的功能时，我们发现每个基因都参与了从法呢基二磷酸合成角鲨烯的新途径。
Squalene (SQ) is an intermediate in the biosynthesis of sterols in eukaryotes and a few bacteria and of hopanoids in bacteria where they promote membrane stability and the formation of lipid rafts in their hosts. The genes for hopanoid biosynthesis are typically located on clusters that consist of four highly conserved genes—hpnC, hpnD, hpnE, and hpnF—for conversion of farnesyl diphosphate (FPP) to hopene or related pentacyclic metabolites. While hpnF is known to encode a squalene cyclase, the functions for hpnC, hpnD, and hpnE are not rigorously established. The hpnC, hpnD, and hpnE genes from Zymomonas mobilis and Rhodopseudomonas palustris were cloned into Escherichia coli, a bacterium that does not contain genes homologous to hpnC, hpnD, and hpnE, and their functions were established in vitro and in vivo. HpnD catalyzes formation of presqualene diphosphate (PSPP) from two molecules of FPP; HpnC converts PSPP to hydroxysqualene (HSQ); and HpnE, a member of the amine oxidoreductase family, reduces HSQ to SQ. Collectively the reactions catalyzed by these three enzymes constitute a new pathway for biosynthesis of SQ in bacteria. In determining the functions of three highly conserved genes in bacterial hopanoid gene clusters, we discover that each participates in a new pathway for biosynthesis of squalene from farnesyl diphosphate.