Semialdehyde, amino adipic

Formed from condensation of two a-amino adipic acid 8-semialdehyde residues... 

The numerous cross-linkages found in collagen are the result of the oxidation of lysine and hydroxylysine to a-amino adipic acid 8-semialde-hyde (allysine) and 8-hydroxy a-amino adipic acid 8-semialdehyde (hy-droxyallysine), respectively, following the assemblage of the collagen chains into the macromolecular structure (Equations 4 and 5) ... 

The cross-linkages found in collagen and elastin arise from the non-enzymatic interaction of a-amino adipic acid 8-semialdehyde (AL) and 8-hydroxy a-amino adipic acid 8-semialdehyde (HAL) with another residue of the aldehyde or with lysine, hydroxylysine, or histidine residues located at specific positions in the collagen polypeptide chains. Possible relationships among the different compounds in Table II are shown in Figures 4 and 5 for collagen and elastin. 

In presence of transition metal cations and O2, a large number of phenolics exhibit also an amine oxidase-like activity (Akagawa Suyama, 2001). They convert lysine residues of proteins to a-amino-adipic semialdehyde residues. The oxidative deamination is initiated by the metal-catalyzed autooxidation of the phenolic compounds and by its reaction with the l,l-diphenyl-2-picryl hydrazyl (DPPH) radical, likely owing to the formation of quinine. But their biological significance and importance for plants remain to be understood. 

Pinnell, S. R., and Martin, G. R. (1968) The crosslinking of collagen and elastin Enzymatic conversion of lysine in peptide linkage to a-amino-adipic-6-semialdehyde (allysine) by an extract from bone, Proc. Natl, Acad. Sci, USA 61 708. 

---