FIGURE 2.

Biosynthetic pathway of quinolizidine alkaloids. Quinolizidine alkaloids are synthesized by the decarboxylation of Lys, yielding cadaverine, which is further modified by various reactions as shown. The metabolites derived from the pathway are shown. Enzymes involved in the synthesis of these alkaloids are indicated: LDC, Lys decarboxylase; HMT/HLT, tigloyl-CoA: (–)-13α-hydroxymultiflorine/(+)-13α-hydroxylupanineO-tigloyltransferase; ECT/EFT-LCT/LFT, p-coumaroyl-CoA/feruloyl-CoA: (+)-epilupinine/(–)-lupinine O-coumaroyl/feruloyltransferase.