Purification of human leukocyte elastase and cathepsin G by chromatography on immobilized elastin.

Human leukocyte elastase and cathepsin G were isolated from purulent sputum by a simple procedure involving chromatography on elastin-agarose. Salt extracts of sputum were prepared, treated with DNase, and the precipitate which formed extracted and applied to a column of soluble elastin-Sepharose 4B. Contaminating protein was eluted with 50 mM Tris, 50 mM NaCl, pH 8.0 and then two column volumes of 50 mM acetate, 1.0 M NaCl, pH 5.0. The tightly bound elastase and cathepsin G together with a trypsin-like serine protease could finally be eluted with 50 mM acetate, 1.0 M NaCl, 20% DMSO, pH 5.0. Resolution of the proteases was accomplished by cation-exchange chromatography. Disc gel electrophoresis established the purity of elastase and cathepsin G and confirmed the existence of several isozymes for each.