hydroxylysinecontaining

Hydroxylysine-containing refers to molecules, typically proteins or peptides, that include hydroxylysine residues. Hydroxylysine is a post-translationally modified form of lysine, produced by the hydroxylation of lysine residues through lysyl hydroxylase enzymes that require vitamin C (ascorbate), iron, and α-ketoglutarate. The modification is especially prominent in extracellular matrix (ECM) proteins such as collagen and, to a lesser extent, elastin and basement membrane components.

In collagen, hydroxylysine residues can undergo glycosylation, forming galactosylhydroxylysine and glucosylgalactosylhydroxylysine. These glycosylations influence collagen folding, stability, and interactions within the ECM. Hydroxylysine also serves as a precursor in cross-link formation. Lysyl oxidase oxidizes the ε-amino groups of hydroxylysine (and sometimes lysine) to create reactive aldehydes that participate in covalent cross-linking, yielding mature, long-lasting cross-links such as hydroxylysyl pyridinoline and lysyl pyridinoline. These cross-links contribute to the tensile strength and structural integrity of connective tissues.

Deficiencies in the enzymes responsible for hydroxylysine modification or in vitamin C can impair collagen maturation, leading to connective tissue abnormalities. Age-related changes and tissue-specific differences in cross-linking patterns also affect hydroxylysine-containing proteins, influencing tissue mechanics and function. Analytical approaches include amino acid analysis after acid hydrolysis, mass spectrometry to detect hydroxylysine-containing peptides or cross-links, and immunodetection of glycosylated hydroxylysine forms.

As a category, hydroxylysine-containing encompasses proteins and peptides that bear hydroxylysine residues. The term is used primarily in biochemistry and structural biology to describe the presence and role of this modification in ECM biology, tissue mechanics, and related diseases.