Lois L M, Campos N, Putra S R, Danielsen K, Rohmer M, Boronat A
Departament de Bioquímica i Biologia Molecular, Facultat de Química, Universitat de Barcelona, Martí i Franqués 1, 08028-Barcelona, Spain.
Proc Natl Acad Sci U S A. 1998 Mar 3;95(5):2105-10. doi: 10.1073/pnas.95.5.2105.
For many years it was accepted that isopentenyl diphosphate, the common precursor of all isoprenoids, was synthesized through the well known acetate/mevalonate pathway. However, recent studies have shown that some bacteria, including Escherichia coli, use a mevalonate-independent pathway for the synthesis of isopentenyl diphosphate. The occurrence of this alternative pathway has also been reported in green algae and higher plants. The first reaction of this pathway consists of the condensation of (hydroxyethyl)thiamin derived from pyruvate with the C1 aldehyde group of D-glyceraldehyde 3-phosphate to yield D-1-deoxyxylulose 5-phosphate. In E. coli, D-1-deoxyxylulose 5-phosphate is also a precursor for the biosynthesis of thiamin and pyridoxol. Here we report the molecular cloning and characterization of a gene from E. coli, designated dxs, that encodes D-1-deoxyxylulose-5-phosphate synthase. The dxs gene was identified as part of an operon that also contains ispA, the gene that encodes farnesyl-diphosphate synthase. D-1-Deoxyxylulose-5-phosphate synthase belongs to a family of transketolase-like proteins that are highly conserved in evolution.
多年来，人们一直认为所有类异戊二烯的共同前体异戊烯基二磷酸是通过众所周知的乙酸/甲羟戊酸途径合成的。然而，最近的研究表明，一些细菌，包括大肠杆菌，使用一种不依赖甲羟戊酸的途径来合成异戊烯基二磷酸。在绿藻和高等植物中也报道了这种替代途径的存在。该途径的第一步反应是由丙酮酸衍生的（羟乙基）硫胺素与3-磷酸-D-甘油醛的C1醛基缩合，生成5-磷酸-D-1-脱氧木酮糖。在大肠杆菌中，5-磷酸-D-1-脱氧木酮糖也是硫胺素和吡哆醇生物合成的前体。在此，我们报道了来自大肠杆菌的一个名为dxs的基因的分子克隆和特征分析，该基因编码5-磷酸-D-1-脱氧木酮糖合酶。dxs基因被鉴定为一个操纵子的一部分，该操纵子还包含ispA，即编码法呢基二磷酸合酶的基因。5-磷酸-D-1-脱氧木酮糖合酶属于一类在进化中高度保守的转酮醇酶样蛋白家族。
