Covalent linkage of carboxypeptidase G2 to soluble dextrans--I. Properties of conjugates and effects on plasma persistence in mice.

The covalent attachment of the therapeutic enzyme carboxypeptidase G2 to soluble dextrans of varying molecular weight resulted in a 5-15-fold increase in plasma persistence in normal and tumour-bearing mice. The molecular weight of the dextran used markedly affected the number of dextran molecules present in the conjugate, resulting in a molecular weight distribution between 6 and 12 X 10(5) daltons. The isoelectric point of the conjugates varied between 4.1 and 4.8 compared to native enzyme 7.8. Conjugates were resistant to proteolysis by trypsin and chymotrypsin, but showed little difference in their affinity for substrate.