Purification and characterization of a serine proteinase inhibitor from human articular cartilage

An inhibitor of serine proteinases from human articular cartilage was purified to homogeneity by sequential ultrafiltration and ion exchange chromatography on CM-Sephadex C-50. The apparent molecular weight of the cationic glycoprotein (pI greater than 10) was determined to be 16.5 X 10(3) by SDS gel electrophoresis. The inhibitor blocked the activity of leukocyte elastase, cathepsin G and trypsin but not leukocyte collagenase. In kinetic studies for the interactions with leukocyte elastase a firm enzyme-inhibitor binding was obtained. Amino acid analyses did not reveal homologies with other serine proteinase inhibitors already purified from human tissues.