Abbrev. K Lys
Full Name Lysine
Side chain type basic
pKr (R) 10.54
Side chain -(CH2)4NH2
Hydro- phobic no
Aromatic or Aliphatic no
van der Waals volume 135
Codon AAA, AAG
Occurrence in proteins (%) 5.9
Remarks: Essential for humans. Behaves similarly to arginine. Contains a long flexible side-chain with a positively-charged end. The flexibility of the chain makes lysine and arginine suitable for binding to molecules with many negative charges on their surfaces. E.g., DNA-binding proteins have their active regions rich with arginine and lysine. The strong charge makes these two amino acids prone to be located on the outer hydrophilic surfaces of the proteins; when they are found inside, they are usually paired with a corresponding negatively-charged amino acid, e.g., aspartate or glutamate.
Lysine is one of the 20 amino acids normally found in proteins. With its 4-aminobutyl side-chain, it is classified as a basic amino acid, along with arginine and histidine. It is an essential amino acid, and the human nutritional requirement is 1–1.5 g daily. A deficiency in lysine can result in a deficiency in niacin (which is a B Vitamin). This can cause the disease pellagra. Lysine can also be used as a nutritional supplement to help against herpes.
Lysine is the limiting amino acid in all cereal grains, but is plentiful in all pulses (legumes). Fish are also quite rich in lysine. Plants that contain significant amounts of lysine include:
Lysine can undergo posttranslational modification in protein molecules, often by methylation or acetylation. Collagen contains hydroxylysine which is derived from lysine. O-Glycosylation of lysine residues in the endoplasmic reticulum or Golgi apparatus is used to mark certain proteins for secretion from the cell.
Lysine is metabolised in mammals to give Acetyl-CoA, via an initial transamination with α-ketoglutarate. The bacterial degradation of lysine yields cadaverine by decarboxylation.
Some individuals have found that taking lysine supplements may reduce the frequency of canker sores.
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