Molecular Mechanism of the Catalytic Function of prenyl Chain Elongating Enzymes Participating in the biosynthesis of Isoprenoid Compounds

在异戊二烯类化合物的生物合成中，所有的碳骨架都是由戊烯基转移酶作用下合成的戊烯基二磷酸酯衍生而来的。在过去的几十年里，许多催化(E)型戊烯基链延长的戊烯基转移酶的结构基因已经被鉴定和表征。然而，直到我们在1998年分离到黄微球菌十一烯基二磷酸合成酶基因之前，还没有关于(Z)-戊烯基二磷酸合成酶结构的信息。(Z)-戊烯基二磷酸合成酶与(E)-戊烯基二磷酸合成酶的氨基酸序列完全不同，其晶体结构在2.2A分辨率下被确定为顺式-戊烯基链延长酶中的第一个三维结构。这种酶显示了一个新的蛋白质折叠，它与与类异戊二烯生物合成相关的酶完全不同，具有共同的…更多的n结构“类异戊二烯合酶折叠”。根据该酶的精确三维结构和定点诱变实验所积累的数据，推导出了该酶与底物结合的合理模型。利用在大肠杆菌中高效表达的重组酶在病毒橡胶生产中发现，橡胶树橡胶转移酶可能需要橡胶树胶乳洗涤底部颗粒部分中的一些激活因子来生产高分子橡胶分子。在高等生物中，Dolicol作为糖基载体脂类在N-连接的糖蛋白和糖基磷脂酰肌醇锚定蛋白的生物合成中起着至关重要的作用。通过数据库搜索编码顺式戊烯基链延长酶高度保守区的基因，我们已经鉴定出一个人脱氢二磷酸合成酶。Northern blotting分析了脱氢二磷酸合酶在人体组织中的表达水平，发现在睾丸和肾脏中都有高水平的表达。较少

In the biosynthesis of isoprenoid compounds all of the carbon backbones are derived from prenyl diphosphates, which are synthesized by the action of prenyltransferases.During the last decades the structural genes for many kinds of prenyltransferases catalyzing (E)-type prenyl chain elongation have been identified and characterized. However, no information has been available about the structures of (Z)-prenyl diphosphate syntheses until our isolation of the gene for Micrococcus luteus undecaprenyl diphosphate synthase in 1998. The amino acid sequence of the (Z)-prenyl diphosphate synthase is totally different from those of (E)-prenyl chain elongating enzymes.The crystal structure of the undecaprenyl diphosphate synthase has been determined at 2.2 A resolution as the first three dimensional structure among cis-prenyl chain elongating enzymes. This enzyme shows a novel protein fold which is completely different from those for the enzymes relating to isoprenoid biosynthesis, having a commo … More n structure "isoprenoid synthase fold". A plausible substrate-binding model of the enzyme has been deduced from the precise three-dimensional structure as well as the data accumulated from site-directed mutagenesis experiments.We have isolated and characterized the cDNA for the rubber transferaes from Hevea brasiliensis. In viro rubber production using the recombinant enzyme overexpressed in E. coli cells revealed that the Hevea rubber transferase might require some activation factors in the washed bottom particle fraction of Hevea latex for the production of high molecular weight rubber molecules.Dolichol has an essential role in the biosynthesis of N-linked glycoproteins and glycosylphosphatidylinositol-anchored proteins as the glycosyl carrier lipid in higher organisms. Through the database search for a gene encoding highly conserved regions for cis-prenyl chain elongating enzymes, we have identified a human dehydrodolichyl diphosphate synthase. The mRNA expression levels of the dehydrodolichyl diphosphate synthase in human tissues were analyzed by Northern blotting to show high expressions in testis as well as in kidney. Less