Trypsin-like neutral protease associated with soluble elastin

Abstract

Isolation of chicken tropoelastin was complicated by the presence of a neutral protease closely associated with tropoelastin that was capable of sequentially degrading tropoelastin to small peptides. Substrate and inhibitor specificities of this neutral protease associated with purified tropoelastin were examined. The enzyme displayed proteolytic activity against casein, and esterase activity was detected when assayed against N-tosyl-L-arginine methyl ester but not against tert-butyloxycarbonyl-L-alanine p-nitrophenyl ester. No appreciable elastinolytic activity was detectable against insoluble sodium dodecyl sulfate treated elastin or maleylated tropoelastin. The enzyme was not inhibited by the chymotrypsin inhibitor toluenesulfonylphenylalanine chloromethyl ketone. The enzyme was inhibited by phenylmethanesulfonyl fluoride and, to various degrees, by metal chelators. Tosyllysyl chloromethyl ketone, .epsilon.-aminocaproic acid and Aprotinin (pancreatic trypsin inhibitor-Kunitz type), all inhibitors of trypsin-like enzymes, were very effective inhibitors, as were soybean trypsin inhibitor and human .alpha.-1-antitrypsin. The tropoelastin-associated enzyme apparently was a neutral serine protease with trypsin-like specificity.