L-Tryptophan is an amino acid precursor of serotonin and melatonin.

Methionine is one of the common sulfur-containing amino acids. Methionine is a common methyl-group donor to various substrates, such as creatine, epinephrine, ergosterol, and choline. L-Methionine is used as an essential amino acid for human development and therapeutically acts as an antidote…

L-histidine is an essential amino acid with a basic side chain, and is hydrophilic in character. It contains an imidazole group in the side chain. Histidine is biosynthesized from ATP, 5-phosphoribosyl-1-pyrophosphate (PRPP), and glutamine. In turn, histidine is degraded to glutamate by histidase,…

L-Glutamine, the uncharged and amidated analog of L-glutamic acid, is an important amino acid for the incorporation of NH4+ into biomolecules. It is biosynthesized from NH4+ and glutamate via the enzyme glutamate synthetase. In turn, degradation of glutamine to free the ammonia moiety is mediated…