The chemistry of connective tissues. 5. The elastase activity of proteolytic enzymes

Abstract

A number of proteolytic and mucolytic enzymes were assayed for elastolytic activity with a preparation of elastin of established purity as substrate. This was prepared from bovine ligamentum nuchae; it contained less than 0.3% of carbohydrate and was free from collagen. In addition to pancreatic elastase, 3 proteolytic enzymes, papain, ficin and bromelin had a high activity towards elastin. Crystalline trypsin, chymotrypsin, pepsin, Rhozyme and preparations of kathepsin from kidney and spleen were either totally inactive or very slow. Preparations of bacterial chondrosulphatase, purified chondroitinase and testicular hyaluronid-ase showed no activity. Preparations of [alpha]-amylase from saliva and cereal seeds were inactive but a crystalline sample of pancreatic [alpha]-amylase showed activity. This disappeared on further recrystallization, and it is concluded that the elastolytic activity of [alpha]-amylase reported in the literature is due to contamination with pancreatic elastase. Various commercial preparations of ficin all showed the same ratio of elastolytic to proteolytic activity as measured by viscosity reduction of gelatin. This same ratio was maintained throughout fractionation and purification of commercial dried fig latex. It was concluded that "fig-latex elastase" is identical with the major proteolytic enzyme in preparations of "ficin". The results of the survey confirm the view that elastolysis is the result of proteolytic activity. The failure of certain well-characterized proteolytic enzymes such as trypsin and chymotrypsin to dissolve elastin is attributed either to their failure to penetrate the cross-linked structure of elastin or to the very restricted peptide-bond specificity exhibited by these enzymes.