<unk>  (abbreviated as<unk>  or<unk> ;<unk>  or Z represents either<unk> tamate or<unk> tamic acid) is one of the 20 amino acids encoded by the standard genetic code. Its side chain is an amide formed by replacing the side-chain hydroxyl of<unk> tamic acid with an amine functional group. It can therefore be considered the amide of the acidic amino acid<unk> tamate. Its codons are CAA and CAG.
Glutamine
Arginine
Choline
Nicotinamide
Cysteamine 
Citrulline
Ethionine
Carnitine