Lysine

Lysine is one of the 20 amino acids normally found in proteins. Its primary amine (4-aminobutyl)functional group is protonated at physiological pH (~7.4), allowing it to act as a donor in hydrogen bonding and/or as a general base in catalysis. Other amino acids with these properties include arginine and histidine. It is an essential amino acid, with a human nutritional requirement of 1–1.5 g daily. Used as a dietary supplement, it is claimed that lysine may be useful for those with herpes simplex infections; however, the evidence regarding these benefits is mixed.