Fig. 1

Biosynthesis pathway for limonene production in plants and the yeast Y. lipolytica. Limonene is biosynthesized from the precursor GPP by enzymatic biotransformation with d- or l-limonene synthetase. IPP and DMAPP are converted to GPP in both plant and Y. lipolytica. a Biosynthesis pathway for limonene production in plants. Plants produce GPP via the methylerythritol phosphate pathway from pyruvate and glyceraldehyde-3-phosphate. b Biosynthesis pathway for limonene production in Y. lipolytica. Yeast rely on the mevalonate pathway to produce GPP from acetyl-CoA. Since LS is not present in Y. lipolytica to construct a complete limonene pathway in Y. lipolytica, two heterologous genes encoding d-limonene synthase (dLS, from C. limon) and l-limonene synthase gene (lLS, from M. spicata) were introduced (shown in red). And downstream metabolic pathways of limonene may lie in yeast (shown in blue). The endogenous MVA pathway enzymes (purple) that were overexpressed in the engineered Y. lipolytica strains. Enzymes involved in the MEP pathway in plants and in the MVA pathway in Y. lipolytica are shown in parentheses. Homologous enzymes found in Y. lipolytica are shown in purple. DXPS DXP synthase, DXPRI DXP-reductoisomerase, MEPCT MEP cytidylyltransferase, CDP-MEK CDP-ME kinase, MECDPS MECDP-synthase, HMBPPS (E)-4-hydroxy-3-methylbut-2-enyl-diphosphate synthase, HMBPPR HMBPP reductase, IPPDI isopentenyl-diphosphate delta-isomerase, GPPS geranyl-diphosphate synthase, lLS l-limonene synthase, dLS d-limonene synthase, ACOAAT1 acetyl-CoA C-acetyltransferase 1, ACOAAT2 acetyl-CoA C-acetyltransferase 2, HMGS hydroxymethylglutaryl-CoA synthase, HMGR hydroxymethylglutaryl-CoA reductase, MK mevalonate kinase, PMK phosphomevalonate kinase, PMVADO diphosphomevalonate decarboxylase, IPPDI isopentenyl-diphosphate delta-isomerase, GGPPS geranylgeranyl diphosphate synthase, type III, FPPS farnesyl diphosphate synthase