Human skin chymotryptic proteinase. Isolation and relation to cathepsin G and rat mast cell proteinase I

A chymotrypsin-like proteinase was purified 2400 fold from human skin. The procedure involves extraction of the proteinase from skin in 2 M KCl, precipitation with protamine chloride, fractionation by gel filtration chromatography, and fractionation by chromatography using a CH-Sepharose-D-tryptophan methyl ester affinity column. The properties of this proteinase were compared to the rat mast cell proteinase I and human cathepsin G. Differences were observed in the rates at which the proteinases were inhibited by diisopropyl fluorophosphate, the sensitivity of the proteinases to protein proteolytic inhibitors, the relative hydrolytic rates of the proteinases for a series of substrates, and the kinetic constants of the proteinases for synthetic substrates. The human skin proteinase did not react with antiserum to the rat skin proteinase and did not elute in the same position as the rat skin proteinase on gel filtration columns. These data demonstrate that the human skin proteinase is distinct from the other proteinases. Extracts of involved skin from patients with cutaneous mastocytosis had 15-fold higher levels of chymotryptic activity than extracts of uninvolved skin or skin from normal controls. The enzymatic properties of the material extracted from the biopsied skin were similar to those of the proteinase from normal skin, suggesting that the human skin chymotrypsin-proteinase is a mast cell constituent.