Definitions

roman coriander

Lysine

[lahy-seen, -sin]

Lysine (abbreviated as Lys or K) is an α-amino acid with the chemical formula HO2CCH(NH2)(CH2)4NH2. This amino acid is an essential amino acid, which means that humans cannot synthesize it. Its codons are AAA and AAG.

Lysine is a base, as are arginine and histidine. The ε-amino group often participates in hydrogen bonding and as a general base in catalysis. Common posttranslational modifications include methylation of the ε-amino group, giving methyl-, dimethyl-, and trimethyllysine. The latter occurs in calmodulin. Other posttranslational modifications at lysine residues include acetylation and ubiquitination. Collagen contains hydroxylysine which is derived from lysine by lysyl hydroxylase. O-Glycosylation of lysine residues in the endoplasmic reticulum or Golgi apparatus is used to mark certain proteins for secretion from the cell.

Biosynthesis

As an essential amino acid, lysine is not synthesized in animals, hence it must be ingested as lysine or lysine-containing proteins. In plants and microorganisms, it is synthesized from aspartic acid, which is first converted to β-aspartyl-semialdehyde. Cyclization gives dihydropicolinate, which is reduced to Δ1-piperidine-2,6-dicarboxylate. Ring-opening of this heterocycle gives a series of derivatives of pimelic acid, ultimately affording lysine. Enzymes involved in this biosynthesis include:

  1. Aspartokinase
  2. β-aspartate semialdehyde dehydrogenase
  3. Dihydropicolinate synthase
  4. Δ1-piperidine-2,6-dicarboxylate dehydrogenase
  5. N-succinyl-2-amino-6ketopimelate synthase
  6. Succinyl diaminopimelate aminotransferase
  7. Succinyl diaminopimelate desuccinylase
  8. Diaminopimelate epimerase
  9. Diaminopimelate decarboxylase

Metabolism

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.

Synthesis

Synthetic, racemic lysine has long been known. A practical synthesis starts from caprolactam.

Dietary sources

The human nutritional requirement is 1–1.5 g daily. It is the limiting amino acid (the essential amino acid found in the smallest quantity in the particular foodstuff) in all cereal grains, but is plentiful in all pulses (legumes). Plants that contain significant amounts of lysine include:

Good sources of lysine are foods rich in protein including meat (specifically red meat, pork, and poultry), cheese (particularly Parmesan), certain fish (such as cod and sardines), and eggs.

Properties

L-Lysine is a necessary building block for all protein in the body. L-Lysine plays a major role in calcium absorption; building muscle protein; recovering from surgery or sports injuries; and the body's production of hormones, enzymes, and antibodies.

Modifications

Lysine can be modified through acetylation, methylation, ubiquitination, sumoylation, neddylation, biotinylation and carboxylation which tends to modify the function of the protein of which the modified lysine residue(s) are a part.

Clinical significance

It has been suggested that lysine may be beneficial for those with herpes simplex infections. However, more research is needed to fully substantiate this claim. For more information, refer to Herpes simplex - Lysine.

There are Lysine conjugates that show promise in the treatment of cancer, by causing cancerous cells to destroy themselves when the drug is combined with the use of phototherapy, while leaving non-cancerous cells unharmed.

In popular culture

The 1993 film Jurassic Park, which is based on the 1989 Michael Crichton novel Jurassic Park, features dinosaurs that were genetically altered so they could not produce lysine. This was supposed to prevent the cloned dinosaurs from leaving the park, forcing them to depend on lysine supplements provided by the park's veterinary staff. Most vertebrates cannot produce lysine by default (it is an essential amino acid).

The 2002 Max Tundra single "Lysine" (featuring Becky Jacobs) is a tribute to the advantages of lysine.

The Indian children's vitamin tonic, Incremin, was claimed to supply this essential amino acid.

References

See also

Sources

  • Much of the information in this article has been translated from Lysin.

External links

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