Allysine is a derivative of

lysine Lysine (symbol Lys or K) is an α-amino acid that is a precursor to many proteins. Lysine contains an α-amino group (which is in the protonated form when the lysine is dissolved in water at physiological pH), an α-carboxylic acid group ( ...

that features a formyl group in place of the terminal amine. The free amino acid does not exist, but the allysine ''residue'' does. It is produced by aerobic oxidation of lysine residues by the enzyme

lysyl oxidase Lysyl oxidase (LOX), also known as protein-lysine 6-oxidase, is an enzyme that, in humans, is encoded by the ''LOX'' gene. It catalyzes the conversion of lysine residues into its aldehyde derivative allysine. Allysine form cross-links in extr ...

. The transformation is an example of a

post-translational modification In molecular biology, post-translational modification (PTM) is the covalent process of changing proteins following protein biosynthesis. PTMs may involve enzymes or occur spontaneously. Proteins are created by ribosomes, which translation (biolog ...

. The

semialdehyde In organic chemistry, a semialdehyde is a compound containing an aldehyde and a carboxylic acid functional groups. Semialdehydes are common in biochemistry. The simplest semialdehydes have the formula . As illustrated by the behavior of the smalle ...

form exists in equilibrium with a cyclic derivative. PTMofLysine

Allysine is involved in the production of

elastin Elastin is a protein encoded by the ''ELN'' gene in humans and several other animals. Elastin is a key component in the extracellular matrix of gnathostomes (jawed vertebrates). It is highly Elasticity (physics), elastic and present in connective ...

and

collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

. Increased allysine concentration in tissues has been correlated to the presence of fibrosis. Allysine residues react with sodium 2-naphthol-6-sulfonate to produce a

fluorescent Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with color ...

bis-naphtol-allysine product. In another assay, allysine-containing proteins are reduced with sodium borohydride to give a peptide containing the 6-hydroxynorleucine (6-hydroxy-2-amino caproic acid) residue, which (unlike allysine) is stable to proteolysis.

References

Alpha-Amino acids Aldehydes Aldehydic acids {{Biochemistry-stub

Further reading

See also

References