Collagen Cross-linking

Abstract

The enzyme-dependent production of cross-linked collagen and the lysine-derived cross-link precursor allysine (α-aminoadipic δ-semialdehyde) has been demonstrated. The enzyme, lysyl oxidase, was extracted from embryonic chick cartilage and was inhibited by the lathyrogen β-aminopropionitrile. Cross-linking of collagen was indicated by production of a β12 component of collagen and insoluble collagen in the samples incubated with lysyl oxidase. Allysine production was observed in both α1 and α2 chains. Approximately three times as much was present in the α1 as in the α2 chain. The only lysyl residue that was found to be converted to allysine in the α1 chain was Residue 9 from the amino-terminal end. Since this is the residue that is converted in vivo and β-aminopropionitrile inhibits the conversion in vivo, it is concluded that lysyl oxidase is the physiologically active enzyme necessary for the first step in the cross-linking of collagen.