Abstract
We found urokinase-cofactor (UK-cofactor) which directly increased UK or plasminogen activator activity and purified it from plasma using lysine-Sepharose, salting out, DEAE Sephadex A-50, Sephadex G-100, hydroxyapatite and Amberlite CG-50. However, it remained unclear whether the UK-cofactor acted enzymatically on UK. In the present paper, further characterization of UK-cofactor was performed by the experiments of the reaction between UK and UK-cofactor, and the influence of BAEE (benzoyl arginine ethyl ester) on UK-cofactor were examined.
HMW-UK and UK-cofactor, and LMW-UK and UK-cofactor were incubated at 37°C for 1, 5 and 10min, respectively, then electrophoresed. The UK antigen was not disappeared by incubating with UK-cofactor. The UK-cofactor did not form a precipitaing arc against anti UK-serum. The reaction between UK and UK-cofactor was examined using SDS-PAGE. HMW-UK and UK-cofactor, LMW-UK and UK-cofactor were incubated at 37°C for 1, 5 and 10min, respectively, and the changes of their molecular weights were monitored by SDS-PAGE. HMW-UK was gradually degraded to LMW-UK by UK-cofactor. LMW-UK also degraded to the lower molecular weight protein. It was revealed that the UK-cofactor was not actually a cofactor but a protease which degraded HMW-UK to LMW-UK and to small fragments. This protease was termed UK-converting protease in stead of UK-cofactor. BAEE (2mM) almost inhibited the degradation of UK by UK-cofactor. It is concluded that UK-cofactor is a new protease (UK-converting protease) which degrades HMW-UK to LMW-UK.
