A proteinase (EC 3.4.-.-) active at physiological pH has been isolated from human skin utilizing gel filtration and affinity chromatography techniques. The proteinase has a molecular weight of approx. 28 000 and it is inhibited by α2-macroglobulin, α1-antitrypsin, C 1 ̄ inactivator, soybean trypsin inhibitor and diiosopropyl fluorophosphate. Injection of 1 ng of purified proteinase into rabbit skin induces polymorphonuclear leukocyte infiltration of the cutis. Inhibition of enzyme activity with diisopropyl fluorophosphate inhibits the chemotactic effect. Addition of 0.2 μg/ml of purified proteinase to fibroblast cultures kills the cells within minutes. This proteinase may play a significant role in modulating the inflammatory response after cellular injury.
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