Digestion of elastin by porcine pancreatic elastase I and elastase II

Elastin was fully solubilized by digestion with elastase I or elastase II. Each digest was separated into high‐molecular weight and low‐molecular weight fractions that were characterized by the correspondence to their amino acid content, N‐terminal sequence and C‐terminal amino acids. It was found that although the relative amount of amino acids in the low‐molecular weight fraction obtained by digestion with elastase I was lower than in digestion with elastase II, no major difference in the type of bonds cleaved in the low‐ or high‐molecular weight fractions of each digest could be seen. There is, however, a remarkable difference in the type of bond cleaved by the two enzymes. While elastase I cleaves mostly Ala‐Ala and also Ala‐Gly bonds, elastase II hydrolyzes Leu‐Ala, Leu‐Gly, Phe‐Ala, Phe‐Gly and Tyr‐Ala, Tyr‐Gly bonds. Theoretical calculations led us to suggest both digests are composed of cross‐linked peptides that vary not only in the molecular size but also in the number of cross‐links found in peptides of the same size.