Human pancreatic carboxypeptidase B. I. Isolation, purification, and characterization of fraction II.

Human carboxypeptidase B fraction II has been purified from pancreatic juice by DEAE-'Sephadex' chromatography, isoelectric focusing, and 'Sephadex' G-100 gel filtration. The enzyme has been characterized by analytical polyacrylamide disc-gel electrophoresis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, amino acid analysis Km determination, molecular weight determination on 'Sephadex' G-100, zinc analysis, and inhibition by metal chelating agents. Human carboxypeptidase B fraction II appeared homogeneous in analytical polyacrylamide disc-gel electrophoresis, but showed two components of 23,500 and 9,200 daltons in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Zinc analysis revealed 0.96 gram atoms of zinc per mole of enzyme, and a Km of 65 +/- 3 muM was determined for hydrolysis of hippuryl-L-arginine.