THROMBOLYTIC PROPERTIES OF PROUROKINASE MUTANTS WITH MUTATION IN THE EPIDERMAL GROWTH FACTOR-LIKE DOMAIN

In an attempt to retard the rapid clearance rate of pro-urokinase (pro-UK), we prepared pro-UK mutants (m-pro-UK) with a mutation in the epidermal growth factor-like domain. These comprised of three deletion mutants (del pro-UK) and 14 amino acid-substituted mutants (sub pro-UK), This paper describes the thrombolytic properties of m-pro-UKs in comparison with those of pro-UK. In human plasma clot lysis assay, del pro-UKs had shown much less plasma clot lysis activity than pro-UK, while 7 out of 14 sub-pro-UKs showed activity comparable to that of pro-UK. In the present experiment, all m-pro-UKs were i.v. injected as a bolus to rats with pulmonary embolism, Eight of the sub pro-UKs showed significantly higher thrombolysis than pro-UK, whereas del pro-UKs caused slightly less thrombolysis, The two sub pro-UKs G38K and N32P, in which glycine at 38th position and asparagine at 32nd position were replaced by lysine and proline respectively, showed the most marked thrombolytic effect in the rat model, Their efficacy was then tested in a rabbit model of arterio-venous shunt thrombosis through injection as a bolus, Both were also found to have significantly higher thrombolytic activities than pro-UK in the rabbit model. Sub pro-UK's having higher thrombolytic activity than pro-UK were divisible into two groups: those with prolonged half-lives and those with undiminished or enhanced fibrin/celite affinity,