Scheme of betalain biosynthesis in hairy root
culture. Enzymatically catalyzed steps: E IA, hydroxylating activity of
tyrosinase; E IB, oxidizing activity of tyrosinase; E II, Dopa
dioxygenase; E III, Dopa decarboxylase; E IV, glucosyltransferase.
Spontaneous steps: V, cyclization reactions; and VI, condensation
reactions (aldimine formation). Compound numbers of this scheme
correspond to peak numbers in Figures 2, 6, 7, and 9.