Biochemistry
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Elastin contains a number of cross-linking amino acid residues such as desmosine and isodesmosine which are primarily hydrophobic in character, but have a positively charged pyridinium ring. These cross-linking residues are formed by the action of lysyl oxidase upon Lys residues in tropoelastin, a precursor of elastin. A series of tetrapeptide 4-nitroanilides which contain Lys and a series of modified lysine residues were synthesized. ⋯ Except for two substrates with P2 hydrophobic residues (Bz and Pic), PP elastase was less reactive toward the substrates containing model desmosine residues than toward MeO-Suc-Ala-Ala-Pro-Val-NA. The data support the hypothesis that HL elastase cleaves elastin selectively ner cross-linking residues. The results also indicate that HL elastase binds tightly to these regions and would be poorly effective toward regions of elastin or tropoelastin which contain Lys residues.