抄録
Staphylokinase (SAK) expresses plasminogen activator (PA) activity by forming a complex with plasmin. In this report, the interaction of nonadecapeptide derived from staphylokinase with plasminogen, was investigated. The effects of synthetic peptides on plasminogen activation were estimated by using a chromogenic substrate assay and 125I-labeled plasma clot lysis assay. The binding of peptides to Glu-plasminogen was estimated by using IAsys resonant mirror biosensor. The synthetic nonadecapeptide (SAK22-40) corresponding to Glu22-Leu40 of SAK amino acid sequence did not show any PA activity in the presence of plasmin. However, SAK22-40 enhanced Glu-plasminogen activation by t-PA. SAK22-40 bound to plasminogen in a concentration-dependent manner. Although this binding ability was not inhibited in the presence of anti-K1-K3 (plasminogen fragment containing kringle 1 to 3 domains) IgG or anti-K4 (plasminogen fragment containing kringle 4 domain) IgG, it was partially inhibited by anti- mini plasminogen IgG. The substitution of Lys35 to Ala in SAK22-40 did not show the enhancement of PA activity by t-PA. The t-PA activity was enhanced in the presence of cultured endothelial cells, and it was further enhanced by SAK22-40. These findings indicate that the synthesized nonadecapeptide, SAK22-40, binds to B-chain of Glu-plasminogen and enhances PA activity by t-PA. The mechanism by which SAK22-40 enhances t-PA activity seems to be different from that by which COOH-terminal Lys of fibrin does. [J Physiol Sci. 2006;56 Suppl:S77]
