Glutamine
Glutamine (symbol Gln or Q) is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral, polar amino acid. It is non-essential and conditionally essential in humans, meaning the body can usually synthesize sufficient amounts of it, but in some instances of stress, the body's demand for glutamine increases, and glutamine must be obtained from the diet. It is encoded by the codons CAA and CAG.
Tryptophan synthase
Tryptophan synthase is commonly found in Eubacteria, Archaebacteria, Protista, Fungi, and Plantae. It is absent from animals such as humans. Tryptophan is one of the twenty standard amino acids and one of nine essential amino acids for humans. As such, tryptophan is a necessary component of the human diet.