PHYSICOCHEMICAL CHARACTERIZATION OF PEG-PPG CONJUGATED HUMAN UROKINASE

Human urokinase (UK) was conjugated with polyethylene glycol-polypropy lene glycol (PEG-PPG) and its physicochemical properties were examined . PEG-PPG modification decreased the activity for plasminogen activati on, but increased the half-life of this protein when injected intraven ously in rabbits. Kinetic analysis of PEG-PPG conjugated UK (PEG-PPG-U K) revealed that the kcat for plasminogen activation decreased 1/5-fol d with the increase of K-m in comparison with that of UK, although the se parameters for cleavage of synthetic substrate (S-2444) did not cha nge. However, the inhibitor constant of PEG-PPG-UK for plasminogen act ivator inhibitor 1 (PAI 1) was equal to that of UK. Peptide mapping an alysis revealed that PEG-PPG binding sites were mainly determined to b e Lys 35, 46, 61, 98, 120 and 135 in A-chain and Lys 211, 300, 318, 33 8, 348, 383 and 404 in B-chain. In addition, the modification rates of A and B-chain were 37.8% and 19.8% on average, respectively.