RP-HPLC analysis of the product spectrum synthesized by rPfFPPS. The enzymatic reactions (Protocol II) and RP-HPLC procedure were performed as described in the Methods section. A) [4-14C]IPP and DMAPP; B) [4-14C]IPP and GPP; C) [4-14C]IPP and FPP; D) [1-3H]FPP and IPP. Arrows indicate the co-elution positions of isoprenoid standards. The retention times of GPP, FPP and GGPP were identified by co-injection of commercial standards.