A synthetic peptide derived from staphylokinase enhances plasminogen activation by tissue-type plasminogen activator.

Background: A synthetic nonadecapeptide (SP; GPYLMVNVTGVDGKGNELL) previously enhanced the activation of plasminogen by the SAK/plasmin complex.
Objectives: To identify the binding site for SP on plasminogen and elucidate the effects of SP on plasminogen activation by the tissue-type plasminogen activator (t-PA).
Methods: The effects of SP on plasminogen activation were estimated using a chromogenic substrate and from the cleavage of plasmin on SDS-PAGE under reduced conditions. The binding to SP of various peptides derived from the amino acid sequence of plasminogen was analyzed with an IAsys biosensor. The SP-mediated structural change to plasminogen was analyzed by circular dichroism (CD) spectroscopy. The thrombolytic effects of SP were examined using a mouse model of thrombosis.
Results: SP enhanced the activation of plasminogen by t-PA. The catalytic efficiency (k(cat)/K(m)) of Glu-plasminogen activation by t-PA was 11.4-fold higher in the presence than absence of SP. The binding of SP to plasminogen was greatly inhibited by a synthetic peptide, FEKDKYILQGVTSWGLG, located close to the C-terminal of the plasminogen B region. Near-ultraviolet CD spectra of the complex between SP and Glu-plasminogen significantly differed from those of Glu-plasminogen. When SP was administered in a mouse model of thrombosis, early recanalization was observed in a dose-dependent manner. However, SP did not cause recanalization in t-PA gene-deficient mice.
Conclusions: SP bound to the B region and promoted the activation of plasminogen by t-PA, and then induced effective thrombolysis.
(© 2011 International Society on Thrombosis and Haemostasis.)