Fig. 1.

Melatonin synthesis pathways in different species. (A) Biosynthetic pathway in plants. (B) Biosynthetic pathway in animals. AADC, aromatic amino acid decarboxylase; AcCoA, acetyl coenzyme A; ASMT, acetylserotonin-O-methyltransferase; BH3OH, 4α-hydroxytetrahydrobiopterin; BH4, (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin; CoA, coenzyme A; COMT, caffeic acid-O-methyltransferase; HIOMT, hydroxyindole-O-methyltransferase; PLP, pyridoxal 5-phosphate; PMP, pyridoxamine phosphate; SAH, S-adenosyl homocysteine; SAM, S-adenosyl methionine; SNAT, serotonin N-acetyltransferase; T5H, tryptamine 5-hydroxylase; TDC, tryptophan decarboxylase; TPH, tryptophan hydroxylase.