ELASTIN DEGRADATION BY MATRIX METALLOPROTEINASES - CLEAVAGE SITE-SPECIFICITY AND MECHANISMS OF ELASTOLYSIS

Insoluble elastin was used as a substrate to characterize the peptide bond specificities of human (HME) and mouse macrophage elastase (MME) and to compare these enzymes with other mammalian metalloproteinases a nd serine elastases, New amino termini detected by protein sequence an alysis in insoluble elastin following proteolytic digestion reveal the P'(1) residues in the carboxyl-terminal direction from the scissile b ond, The relative proportion of each amino acid in this position refle cts the proteolytic preference of the elastolytic enzyme, The predomin ant amino acids detected by protein sequence analysis following cleava ge of insoluble elastin with HME, MME, and 92-kDa gelatinase were Leu, Ile, Ala, Gly, and Val, HME and RIME were similar ill their substrate specificity and showed a stronger preference for Leu/Ile than did the 92-kDa enzyme, Fibroblast collagenase showed no activity toward elast in, The amino acid residues detected in insoluble elastin following hy drolysis with porcine pancreatic elastase and human neutrophil elastas e were predominantly Gly and Ala, with lesser amounts of Val, Phe, Ile , and Leu, There were interesting specificity differences between the two enzymes, however, For both the serine and matrix metalloproteinase s, catalysis of peptide bond cleavage in insoluble elastin was charact erized by temperature effects and water requirements typical of common enzyme catalysed reactions, even those involving soluble substrates. In contrast to what has been observed for collagen, the energy require ments for elastolysis were not extraordinary, consistent with cleavage sites in elastin being readily accessible to enzymatic attack.