Functional Study of Streptokinase Mutants

• Main Authors: Ou, Chung-pei, 歐昌沛
• Other Authors: Wu Hua-Lin
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/02838848545815335999

碩士 === 國立成功大學 === 生物化學研究所 === 85 === Streptokinase(SK) is an exoprotein of b-hemolytic streptococcus and is efficient as activator of plasminogen. SK is widely used as a thrombolytic agent in treatment of myocardial infarction. Administration of SK results in generation of plasmin in vascular system. By the action of plasmin, SK resolves clot indirectly. The mechanism whereby SK activates HPlg(human Plg) is not well studied yet. For developing new thrombolytic agent, SK variants were constructed and assayed. The sensitiveness of Lys59-Ser60 bond to the hydrolysis by plasmin has been reported(Shi et al, 1994), and the activity of the truncated SK molecule decreased. Two SK mutants, SKA59 & SKG59, were cloned. The lytic activity of mutants, both in casein and hole blood clot , was better than wildtype SK. It infers that the replacement of Plm sensitive sequence can prolong the activity of SK. Three variants, SKA48,51,53, SKA92,95,96 & SKA111,112,115, were used to probe function of the NH2 terminal in the activation mechanism. The average kinetic parameter, kplg/Kplg, is about 20% of the original, and activation activity were 30% or less of that of native SK. When mixed at 1:1 molar ratio, out of expectation, the variants quickly convert Plg to Plm(less than 1min). A model was proposed that SKA48,51,53, SKA92,95,96may have defect in substrate Plg activation and SKA111,112,115 may promote the transition state complex formation in activation of Plg moiety of SK-Plg complex。