The methylerythritol phosphate pathway contributes to carotenoid but not phytol biosynthesis in Euglena gracilis

The biosynthesis of diadinoxanthin and β-carotene in Euglena gracilis was examined using [1-13C]-d-glucose and [5,5-2H2]-1-deoxy-d-xylulose. In contrast to previous studies on isoprenoid biosynthesis in E. gracilis, the results demonstrate a role for the methylerythritol phosphate (MEP) pathway, along with the mevalonate pathway, in carotenoid biosynthesis. Interestingly, the MEP pathway is not involved in the biosynthesis of phytol, a result not previously observed for other chloroplast-containing organisms.