Figure 1

Shikonin biosynthesis pathway as adopted and modified from Inouye et al. [38]. Encircled numbers represent enzyme catalyzing the corresponding reaction step as follows: 1 ACTH: acetoacetyl-CoA thiolase; 2 HMGS: 3-hydroxy-3-methylglutaryl-CoA synthase; 3 HMGR: 3-hydroxy-3-methylglutaryl-CoA reductase; 4 MVK: mevalonate kinase; 5 PMVK: phosphomevalonate kinase; 6 MVDD: mevalonate diphosphate decarboxylase; 7 IPPI: isopentenyl pyrophosphate isomerase; 8 GDPS: geranyl diphosphate synthase; 9 1-deoxy-D-xylulose 5-phosphate synthase; 10 1-deoxy-D-xylulose 5-phosphate reductoisomerase; 11 2-C-methylerythritol 4-phosphate cytidyl transferase; 12 4-(cytidine-5'-diphospho)-2-C-methylerythritol kinase; 13 2-C-methylerythritol-2,4-cyclophosphate synthase; 14 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate synthase; 15 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase; 16 PAL: phenylalanine ammonia lyase; 17 C4H: cinnamic acid 4-hydroxylase; 18 4-CL: 4-coumaroyl-CoA ligase; 19 PGT: p-hydroxybenzoate -m-geranyltransferase.