Human α-1-antichymotrypsin: purification and properties

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Abstract
Human .alpha.-1-antichymotrypsin was purified to homogeneity by the following sequential steps.sbd. ammonium sulfate fractionation; chromatography on Cibacron Blue Sepharose at pH 7.0; and chromatography on SP-Sephadex C-50 at pH 5.5. The inhibitor has a MW near 68,000 and contains approximately 26% carbohydrate. .alpha.-1-Antichymotrypsin has an amino-terminal arginine and a carboxy-terminal glycine. It also has some homology with .alpha.-1-PI (proteinase inhibitor) based on amino-terminal sequence analysis of both proteins. Complexes of .alpha.-1-antichymotrypsin with human chymotrypsin and human leukocyte cathepsin G are stable in sodium dodecyl sulfate and have MW near 90,000, suggesting 1:1 complex formation on a molar basis between inhibitor and enzyme.