Lysylreste

Lysylreste is a biochemical term used to refer to a lysine residue within a protein or peptide. Derived from the amino acid lysine, a lysylreste is identified by the single-letter code K or the three-letter code Lys. The lysine side chain features an ε-amino group that is positively charged at physiological pH, enabling salt bridges, hydrogen bonding, and site-specific chemistry.

In biology, lysine residues are common targets for post-translational modifications, including acetylation, mono-, di-, and tri-methylation, ubiquitination, and sumoylation. Such modifications regulate protein function, interactions, localization, and stability. Lysyl residues are also involved in cross-linking processes in the extracellular matrix. Enzymatic oxidation by lysyl oxidase converts select lysine residues to reactive aldehydes (allysine), which subsequently form covalent cross-links that reinforce collagen and elastin networks.

Lysine residues can serve as proteolytic cleavage sites for certain proteases, notably trypsin, which cleaves on the C-terminal side of lysine or arginine residues. In proteomics and mass spectrometry, identifying lysylreste and its modifications helps map protein structures and functions.

The term Lysylreste is used as a neutral descriptor rather than to denote a single unique molecule; its significance depends on the protein context and the biochemical processes acting on lysine residues. See also lysine, amino acid residues, post-translational modifications, lysyl oxidase, and cross-linking in collagen and elastin.