Biosynthesis of indolic compound in plants and animals. The essential amino acid tryptophan arises from the shikimate pathway via
chorismate/anthranilate, whereas the other aromatic amino acids, phenylalanine and tyrosine, come from prephenate/arogenate branching and
lead to phenylpropanoids. Tryptophan is converted to 5-hydroxytryptophan and, subsequently, to serotonin, from which melatonin is synthesized
by HIOMT, in both animals and plants. Indole-3-acetic acid synthesis, by tryptophan decarboxylase, is exclusive to plants and leads to tryptamine
precursors.