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. 2021 Jul 14;19(7):e3001326. doi: 10.1371/journal.pbio.3001326

Fig 1. The betalain biosynthetic pathway.

Fig 1

A simplified schematic representation of the main enzymatic and spontaneous reactions leading to the formation of red/purple betacyanins and yellow betaxanthins. Enzymatic steps: (1) tyrosine hydroxylation to ʟ-DOPA catalysed by CYP76AD cytochrome P450 enzymes; (2) cleavage of ʟ-DOPA to form betalamic acid by DODA; (3) ʟ-DOPA oxidation to cyclo-DOPA by CYP76AD1; and (4) cyclo-DOPA glycosylation to cyclo-DOPA 5-O-glucoside by the enzyme cDOPA5GT. S*, spontaneous reaction. Betacyanins are represented as a molecule of betanin. cDOPA5GT, cyclo-DOPA 5-O-glucosyltransferase; cyclo-DOPA, cyclo-dihydroxyphenylalanine; DODA, ʟ-DOPA-4,5-dioxygenase; ʟ-DOPA, 3,4-dihydroxy-ʟ-phenylalanine.