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

Acid-activated human plasma kallikrein (HuPK) was purified from human Cohn fraction IV by affinity chromatography, using a 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-acyl-naphthylamides. 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.