2AA-GPP is an ineffective substrate for UPPSEc and UPPSVv. HPLC analysis of 2AA-GPP with (1, red) UPPSBf, (2, black) UPPSEc, and (3, blue) UPPSVv at (A) 167 nM and (B) 1.7 µM. Chromatograms 2 and 3 are offset by 2 and 4 min, respectively. Note that the peaks representing flow-through material in panel B (2AA-GPP) are cut to give the best view of long chain isoprenoid products. In all chromatograms, the ESI-MS-identified product is indicated below the time axis with the number of Z-configuration isoprenes associated with each peak.