IMMUNOCHEMICAL PROPERTIES AND MOLECULAR FORMS OF UROKINASE

1. By the double immunodiffusion technique, highly purified high molecular weight urokinase (HMW-UK; MW 53,000, 124,000 IU/mg protein) and low molecular weight urokinase (LMW-UK; MW 32,000, 230,000 IU/mg protein) revealed the same antigenicity, and their fibrinolytic activities were equally quenched with rabbit antisera against both enzymes.

2. Specific antisera against the functionally-active HMW-UK heavy chain (H-chain; MW 31,000, 201,000 IU/mg protein) and the HMW-UK light chain (L-chain; MW 18,000) were first prepared. By double immunodiffusion anti H-chain serum reacted to all of the active urokinase species (HMW-UK, LMW-UK and H-chain), whereas anti L-chain serum did not react to any of the active enzymes of low molecular form.

3. Anti H-chain serum quenched the fibrinolytic activities of all of the active enzymes in contrast to anti L-chain serum, which had no effect on LMW-UK and H-chain. Anti L-chain serum was found to exert an anti-fibrinolytic effect on HMW-UK.