Putative pathway for triterpene saponin biosynthesis. Putative pathway for triterpene saponin biosynthesis in P. vietnamensis var. fuscidicus. Two proposed pathways (A and B) for the biosynthesis of ocotillol-type saponins, mainlymajonoside R2 in the horizontally grown rhizome (C) of P. vietnamensis var. fuscidicus
(D). Enzymes found in this study are boxed. Abbreviations: AACT, acetyl-CoA acetyltransferase; β-AS, β-amyrin synthase; DMAPP, dimethylallyl diphosphate; DS, dammarenediol-II synthase; FPP, farnesyl diphosphate; FPPS, farnesyl diphosphate synthase; Glc, glucose; GPP, geranyl pyrophosphate; GGPP, geranylgeranyl diphosphate; GGPPS, geranylgeranyl pyrophosphate synthase; GT, glycosyltransferase; HMG-CoA, 3-hydroxy-3-methylglutaryl coenzyme A; HMGR, HMG-CoA reductase; HMGS, HMG-CoA synthase; IPP, isopentenyl diphosphate; IPPI, IPP isomerase; MVD, mevalonate diphosphate decarboxylase; MVK, mevalonate kinase; P450, cytochrome P450; PMK, phosphomevalonate kinase; SE, squalene epoxidase; SS, squalene synthase.