Department of Applied Molecular Bioscience, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Aichi, Japan.
Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology, Fuchu, 183-8509 Tokyo, Japan.
Proc Natl Acad Sci U S A. 2018 Oct 2;115(40):10034-10039. doi: 10.1073/pnas.1809154115. Epub 2018 Sep 17.
The modified mevalonate pathway is believed to be the upstream biosynthetic route for isoprenoids in general archaea. The partially identified pathway has been proposed to explain a mystery surrounding the lack of phosphomevalonate kinase and diphosphomevalonate decarboxylase by the discovery of a conserved enzyme, isopentenyl phosphate kinase. Phosphomevalonate decarboxylase was considered to be the missing link that would fill the vacancy in the pathway between mevalonate 5-phosphate and isopentenyl phosphate. This enzyme was recently discovered from haloarchaea and certain Chroloflexi bacteria, but their enzymes are close homologs of diphosphomevalonate decarboxylase, which are absent in most archaea. In this study, we used comparative genomic analysis to find two enzymes from a hyperthermophilic archaeon, , that can replace phosphomevalonate decarboxylase. One enzyme, which has been annotated as putative aconitase, catalyzes the dehydration of mevalonate 5-phosphate to form a previously unknown intermediate, -anhydromevalonate 5-phosphate. Then, another enzyme belonging to the UbiD-decarboxylase family, which likely requires a UbiX-like partner, converts the intermediate into isopentenyl phosphate. Their activities were confirmed by in vitro assay with recombinant enzymes and were also detected in cell-free extract from These data distinguish the modified mevalonate pathway of and likely, of the majority of archaea from all known mevalonate pathways, such as the eukaryote-type classical pathway, the haloarchaea-type modified pathway, and another modified pathway recently discovered from .
经修正的甲羟戊酸途径被认为是一般古菌中异戊烯基化合物的上游生物合成途径。该途径的部分鉴定途径被提出，以解释在发现保守酶——异戊烯基磷酸激酶的情况下，磷酸甲羟戊酸激酶和二磷酸甲羟戊酸脱羧酶缺失的谜团。磷酸甲羟戊酸脱羧酶被认为是连接甲羟戊酸 5-磷酸和异戊烯基磷酸之间途径中的缺失环节。这种酶最近从盐杆菌和某些 Chroloflexi 细菌中被发现，但它们的酶与二磷酸甲羟戊酸脱羧酶的密切同源，而大多数古菌中不存在这种酶。在这项研究中，我们使用比较基因组分析从一种高温古菌 中找到了两种可以替代磷酸甲羟戊酸脱羧酶的酶。一种酶被注释为假定的乌头酸酶，它催化甲羟戊酸 5-磷酸的脱水反应，形成一种以前未知的中间产物——-脱水甲羟戊酸 5-磷酸。然后，另一种属于 UbiD-脱羧酶家族的酶，可能需要一个类似 UbiX 的伴侣，将中间产物转化为异戊烯基磷酸。通过体外重组酶测定和细胞游离提取物中的检测，证实了它们的活性。这些数据将 和可能的大多数古菌的经修正的甲羟戊酸途径与所有已知的甲羟戊酸途径区分开来，如真核生物经典途径、盐杆菌型修正途径和最近从 中发现的另一种修正途径。
