Human plasma kallikrein. Preliminary studies on hydrolysis of proteins and peptides

Abstract

Acid-activated human plasma kallikrein (HuPK) was purified from human Cohn fraction IV by affinity chromatography, using as ligand soybean trypsin inhibitor and aminobenzamidine. The purified enzyme does not inactivate bradykinin and lysyl-bradykinin by cleavage of their peptide bonds. Methionyl-lysyl-bradykinin is converted to the more potent peptide, bradykinin, by incubation with plasma kallikrein. The enzyme does not show aminopeptidase activity when assayed with amino-acylnaphthylamides. Arginine-rich polypeptides and proteins, such as polyarginine, salmine, and histones were cleaved by the enzyme. HuPK does not show any detectable caseinolytic activity. A kinin is released from a non-homologous plasma (horse) by this kallikrein. The enzyme is not affected by calcium or EDTA, and it is strongly inhibited by copper ion.