FIG. 1.

The DOXP pathway for biosynthesis of the isoprenoid precursors IPP and DMAPP in E. coli. Gene products implicated in the pathway are boxed. The order of the reactions catalyzed by the products of ygbB, ygbP, and ychB is uncertain. Later reaction steps in the pathway remain to be determined. Note that a gene encoding IPI, although present in E. coli, is not routinely found in organisms that utilize the DOXP pathway (Table 1). The plasmid pAC-LYC (10), shown to the lower right, encodes enzymes (products of the crtE, crtB, and crtI genes) that lead to the synthesis of the pink isoprenoid lycopene from IPP and DMAPP. Cm, chloramphenicol resistance gene; G-3-P, d-glyceraldehyde-3-phosphate; GAPD, glyceraldehyde-3-phosphate dehydrogenase.