Desmosine

4-((4S)-4-Amino-4-carboxybutyl)-1-((5S)-5-amino-5-carboxypentyl)-3,5-bis((3S)-3-amino-3-carboxypropyl)pyridinium

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Desmosine is an amino acid which is formed from four L- lysine molecules. Desmosine and the related isodesmosine are components of the fibrous protein elastin.

Biosynthesis

In the biosynthesis of the desmosine first terminal amino groups of the L -lysine units by the enzyme lysyl oxidase ( EC 1.4.3.13 ) can be oxidized to the corresponding ω - aldehydes. For lysine as Allysin arises. The ring closure to the pyridinium substructure is formed from three allysine units and the amino function of another lysine molecule.

Function

Since desmosine is formally a quadruple amino acid with a central pyridinium ring, it can be used in elastin for cross-linking of protein strands. Desmosine and isodesmosine fluoresce blue under UV light and cause the yellow color of the elastin, its insolubility in water, heat stability and resistance to alkalies and most proteases than elastase.