The 1-deoxy-D-xylulose-5-phosphate pathway of isoprenoid biosynthesis in plants

In plants the biosynthesis of prenyllipids and isoprenoids proceeds via two independent pathways: (a) the cytosolic classical acetate/mevalonate pathw ay for the biosynthesis of sterols, sesquiterpenes, triterpenoids; and (b) the alternative, non-mevalonate l-deoxy-D-xylulose 5-phosphate (DOXP) pathw ay for the biosynthesis of plastidic isoprenoids, such as carotenoids, phyt ol (a side-chain of chlorophylls), plastoquinone-9, isoprene, mono-, and di terpenes. Both pathways form the active C-5-unit isopentenyl diphosphate (I PP) as the precursor from which. all other isoprenoids are formed via head- to-tail addition. This review summarizes current knowledge of the novel 1-d eoxy-D-xylulose-5-phosphate (DOXP) pathway for isopentenyl diphosphate bios ynthesis, apparently located in plastids. The DOXP pathway of IPP formation starts from D-glyceraldehyde-3-phosphate (GA-3-P) and pyruvate, with DOXP- synthase as the starting enzyme. This pathway provides new insight into the regulation of chloroplast metabolism.