Urokinase mutant with better fibrin-specificity.

A 150-156 amino acids-deleted single-chain urokinase-type plasminogen activator (dscu-PA) and its recombinant wild-type counterpart (rscu-PA) were both expressed in Escherichia coli. After denaturation and renaturation in vitro, the expressed products were both purified to a single silver-stained band by means of IgG affinity chromatography. After activation by plasmin, similar enzymatic constants based on the hydrolysis of synthetic substrate S2444 by the two-chain molecular forms of dscu-PA and rscu-PA, or native tcu-PA were observed, suggesting that no impairment had been exerted on the catalytic active site of dtcu-PA by the 150-156 amino acids deletion. In both in vitro fibrin-clot and 125I-fibrin sepharose lysis tests, dtcu-PA showed a significantly higher fibrinolytic activity than rtcu-PA or rscu-PA. Hardly any effect on the concentration of fibrinogen in plasma was found in dtcu-PA. It was concluded that dtcu-PA had a higher fibrin specificity and that tcu-PA could be provided with better fibrin specificity by means of mutation.