Figure 8.

A Model for Polyisoprenoid Biosynthesis in the Context of Leaf Isoprenoid Metabolism.

IPP and DMAPP are synthesized by both the cytosolic MVA and plastidial MEP pathways. The formation of trans-prenyl diphosphates from IPP and DMAPP in these respective cellular compartments results in a spatially distinct pool of plant polyisoprenoids: Cytosolic FPP is utilized for dolichol biosynthesis and the plastidial pool of GGPP is the precursor for polyprenol biosynthesis. Polyprenols, as well as other GGPP-derived isoprenoids, are incorporated into the thylakoid membranes and also into the envelope membranes of plastids. Intermediates: farnesyl diphosphate, FPP; glyceraldehyde-3-phosphate, G3P; geranyl diphosphate, GPP; geranylgeranyl diphosphate, GGPP. Dotted lines indicate multiple steps in the biosynthetic pathway. ω and α represent the terminal isoprene units in dolichols and polyprenols.