Modulation of lysyl oxidase activity toward peptidyl lysine by vicinal dicarboxylic amino acid residues. Implications for collagen cross-linking.

The substrate specificity of lysyl oxidase has been explored with synthetic oligopeptides. kcat/Km increased with increasing peptide length in Ac-(Gly)n-Lys-(Gly)n-CONH2 (n = 1-5). Using 11-mers as the standard peptide length, Glu immediately N-terminal to Lys increased kcat/Km 8.8-fold over that for the -Lys-Glu- sequence and 4.9-fold over the glutamate-free control. Kinetic constants were significantly less perturbed when Glu was 2 or more residues distant from Lys. Replacement of Glu in -Glu-Lys- with Gln significantly increased Km and lowered kcat/Km. Asp rather than Glu N-terminal to Lys decreased Km similar to that of the -Glu-Lys- 11-mer, although the kcat decreased considerably, indicating that lysyl oxidase responds to the side chain length of vicinal Asp or Glu at this position. -Asp-Glu-Lys- within an 11-mer was not oxidized, although this sequence is oxidized within the N-terminal telopeptide of the alpha 1(I) chain in type I collagen fibrils. Thus, lysyl oxidase exhibits distinct preferences for sequences vicinal to lysine. These results are discussed with respect to a model requiring collagen fibril formation prior to oxidation of lysine in collagen by lysyl oxidase.