Modification of Arginyl Residues in Porcine Carboxypeptidase B.

Functional arginyl residues of porcine carboxypeptidase B were modified with phenylglyoxal, decreasing activity towards peptide substrates and the ester hippurylphenyllactate while enhancing activity towards the ester hippurylargininic acid. Both affinity chromatography on Sepharose-6aminohexanoyl-D-arginine and analysis of the chymotryptic peptides from the modified enzyme reveal heterogeneity in the modification. At least two arginyl, residues are modified, and the sequences of the purified chymotryptic peptides containing these residues are Glu-Leu-Arg-Asp-Lys-Gly-ArgTyr and His-Ala-Arg-Glu-Trp. These peptides are homologous with the peptides containing Arg-276 and Arg-71 of carboxypeptidases A and B, but are not homologous to the sequence around Arg-145 in that enzyme. A tentative explanation is provided for the effect of modification of these residues on the activity of carboxypeptidase B. [ABSTRACT FROM AUTHOR]