Isolation and characterization of four forms of kallikrein from hog pancreas autolysate.

Four forms of kallikrein, designated as I-IV, were isolated from hog pancreas autolysate mainly by chromatographies on Lysine-aminohexyl-Sepharose and on DEAE-Sepharose CL-6B, with yields of 65, 56, 59, and 41 mg, respectively, from 10 kg of the tissue. They were homogeneous on polyacrylamide gel electrophoresis, indistinguishable from each other immunologically and had the same amino acid composition. Kallikreins I, II, and III contained carbohydrate, but kallikrein IV was essentially carbohydrate free. On reduction with mercaptoethanol, each of them produced two polypeptide chains with different molecular weights. The H (heavy) chains from kallikreins I and II were identical, designated as H1. It was a glycoprotein with apparent molecular weight of 21,000, whereas the H chain from III and IV, designated as H2, had a molecular weight of 17,000 and was regarded as an H1 chain devoid of carbohydrate. Likewise, the L (light) chain from kallikreins I and III, designated as L1, was a glycoprotein with an apparent molecular weight of 12,000, whereas L2 from II and IV corresponded to L1 devoid of carbohydrate and had a molecular weight of 8,500. Thus, kallikreins I-IV could be expressed as H1L1, H1L2, H2L1, and H2L2, respectively. They had comparable specific activities and Km values towards synthetic substrates. The isoelectric points of kallikreins I-IV were nearly the same, with values of 4.0-4.1.