Tryptophan (W)

Tryptophan (abbreviated as Trp or W; encoded by the codon UGG) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group, an α-carboxylic acid group, and a side chain indole, classifying it as a non-polar, aromatic amino acid. It is essential in humans, meaning the body cannot synthesize it and thus it must be obtained from the diet. Tryptophan is also a precursor to the neurotransmitter serotonin and the hormone melatonin. Like other amino acids, tryptophan is a zwitterion at physiological pH where the amino group is protonated (–NH3+; pKa = 9.39) and the carboxylic acid is deprotonated ( –COO−; pKa = 2.38).

National Center for Biotechnology Information. PubChem Compound Database, CID= 6305