Identification of a new crosslinking amino acid in elastin

Abstract

Recently, Partridge et al . (1963) described the occurrence in elastin of two hitherto unrecognized amino acids for which evidence has now accrued to show their origin from lysine residues in a “pre-elastin” (Partridge et al ., 1964; Miller et al ., 1964). These substances, called desmosine and isodesmosine, are in fact quaternary pyridinium compounds with four side-chain substituents that function in crosslinking of elastin chains (Thomas et al ., 1964). An examination of peptide fractions of elastin selected for enrichment with respect to the desmosines revealed the presence of an additional amino acid, called X 4′ also previously undescribed (Franzblau et al ., 1965). The present communication presents data to show that X 4 can be represented by the formula, N ϵ-(5-amino 5-carboxypentanyl)-lysine.