Fig. 2. Microfibril and elastic fibre formation. Fibrillin is assembled pericellularly into microfibrillar arrays that appear to undergo time-dependent maturation into beaded transglutaminase-crosslinked microfibrils. Mature microfibrils form parallel bundles that may be stabilised at inter-microfibrillar crosslinked regions. In elastic tissues, tropoelastin is deposited on microfibril bundles, and lysyl oxidase-derived crosslinks then stabilise the elastin core. Crosslinks catalysed by the actions of transglutaminase and lysyl oxidase are shown. Transglutaminase forms -glutamyl-e-lysine isopeptide bonds within or between peptide chains. Lysyl oxidase catalyses the oxidative deamination of certain lysine residues in elastin and subsequent, probably spontaneous, reactions lead to the formation of bifunctional crosslinks (dehydrolysinonorleucine and allysine aldol), a trifunctional crosslink (dehydromerodesmosine), and two tetrafunctional crosslinks (desmosine and isodesmosine, shown here).

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