isodesmosina

Isodesmosine, occasionally rendered as isodesmosina in some languages, is a pyridinium crosslinking derivative formed from four lysine residues in elastin. It is one of the two major crosslinks in mature elastin, the other being desmosine, and together they create the highly interconnected network that gives elastin its characteristic elasticity.

Biochemical formation occurs during elastin maturation when lysyl oxidase converts lysine residues to reactive allysine. These reactive groups condense with other lysine-derived residues to form desmosine and isodesmosine crosslinks, which are tetrafunctional and help link different polypeptide chains. Desmosine and isodesmosine are structural isomers.

Distribution and function vary by tissue and age. Elastin-rich tissues such as arteries, lungs, and skin contain measurable amounts of both crosslinks, and their relative abundance influences the long-term mechanical properties and durability of the tissue. The crosslinks contribute to resilience and durability by linking elastin fibers into a stable, elastic network.

Detection and significance: Isodesmosine, along with desmosine, can be measured in biological samples, notably urine, as a biomarker of elastin breakdown and turnover. Elevated levels can be associated with diseases involving elastin degradation, such as chronic obstructive pulmonary disease, vascular disease, and aging processes. Analytical methods include high-performance liquid chromatography and mass spectrometry, sometimes with immunoassays.

In summary, isodesmosine is a key elastin crosslinker derived from lysine residues, paired with desmosine, and serves as both a structural component and a biomarker of elastin metabolism.