hydroxyallysine

Hydroxyallysine is a hydroxylated derivative associated with allysine, a lysine-derived amino aldehyde that can arise in Maillard-type reactions. In some sources, hydroxyallysine is described as a family of hydroxy-substituted allylsine isomers rather than a single, well-defined compound, reflecting variability in structure depending on source and method of detection. Allylsine itself is formed when reactive aldehydes such as acrolein react with the ε-amino group of lysine residues on proteins, creating covalent adducts that can stabilize as imine or related linkages. Hydroxylation of these adducts yields hydroxyallysine, a modification that may occur under oxidative conditions or through hydroxylation processes mediated by reactive oxygen species or metal-catalyzed reactions.

In biological and food contexts, hydroxyallysine-containing adducts are considered intermediates or markers within complex glycation and lipid peroxidation pathways. They may contribute to protein cross-linking and alterations in protein function, and are often discussed in relation to advanced glycation end products (AGEs) and the chemistry of heat-treated foods.

Analytically, compounds associated with hydroxyallysine are typically detected by liquid chromatography–mass spectrometry, frequently after derivatization to improve stability and ionization. Given the variability in naming and possible isomeric forms, precise reporting of structural identity is important in studies.

See also: allysine, advanced glycation end products, Maillard reaction, lysine adducts.