A new alternative non-mevalonate pathway of isoprenoid biosynthesis in eubacteria and plants

摘要

This review considers the discovery of an alternative non-mevalonate pathway of early stages of isoprenoid biosynthesis leading to isopentenyl diphosphate. This pathway was discovered in experiments with several Eubacteria producing triterpenoids of the hopane series. ~(13)C-Labeled acetate glucose, and triosophosphates were used as precursors. Distribution of ~(13)C-label in isoprenoids was studied by ~(13)C-NMR. In Eubacteria, the universal C_5-precursor, isopentenyl diphosphate, apparently is not formed via the classic acetate/mevalonate pathway but is synthesized via a novel glyceraldehyde-3-phosphate/pyruvate pathway. It was postulated that the condensation of the C_2-unit formed by pyruvate dexarboxylation with C_3-unit (glyceraldehyde-3-phosphate) and subsequent rearrangement results in the formation of the branched C_5-precursor, isopentenyl diphosphate. In algae Scenedesmus obliquus, not only all plastid isoprenoids (carotenoids and prenyl side chains of chlorophyll and plastoquinone-9) but also the non-plastid cytoplasmic sterols axe formed via this novel pathway. In higher plants, the plastid isoprenoids axe formed via the glyceraldehyde/pyruvate pathway, while the cytoplasmic sterols are formed via the acetate/mevalonate pathway.