Streptokinase from haemolytic bacteria, Streptococcus sp., has been known to act as an activator for the conversion of human plasminogen into the catalytically active plasmin (E.C. 3.4.21.7). However, streptokinase itself was found to be inactive catalytically. Rather its complex form with human plasminogen seems to be have a specific hydrolytic activity toward human plasminogen.
Using the synthetic substrate such as N-α-Cbz-L-lysine p-nitrophenyl ester, the activity of streptokinase-human plasminogen complex was determined. A series of experiment were carried out to find out the condition that the streptokinase-human plasminogen complex free from plasmin activity was formed. From the results of experiments it was found that the added streptokinase was fully converted into its active complex in the condition of excess plasminogen with regard to streptokinase, and that so formed complex converted plasminogen to plasmin. Also it was observed that the activity of plasmin so formed was selectively inhibited by soybean trypsin inhibitor. As a result it was recognized that this complex was stoichiometrically formed according to amounts of streptokinase and plasminogen.
The specificity of streptokinase-plasminogen complex for synthetic esters and macromolecules was investigated to obtain a information of active site of active complex. The results indicate that both positively charged and hydrophobic groups in substrate are required for binding capability to the complex. Also it was shown that the complex had a specificity for macromolecules. In addition it was observed that the activity of complex was increased in the presence of human fibrinogen which took a part in blood coagulation mechanism. On the basis of chemical modification study it is suggested that histidine and carboxylic groups are involved in the active site of streptokinase-plasminogen complex.
병원균인 $\underline{Streptococcus}$ sp.의 병원 효소인 스트렙토 카이네이스는 전구 효소인 프라즈미노젠을 활성을 갖는 프라즈민 으로 전환시키는 활성체로서 작용한다고 알려져 있다. 그러나, 스트렙토카이네이스 그 자체는 활성을 갖지 않는 단백질인데 인체 프라즈미노젠과 복합체를 형성함 으로서 다른 분자인 프라즈미노젠에 대하여 특이적인 가수분해 활성을 보이는 것 같다.
우리는 프라즈민의 활성이 없는 스트렙토카이네이즈프라즈미노젠 복합체가 어떤 조건에서 형성될 수 있는지를 N-α-Cbz-L-lysine p-nitrophenyl ester 에 대한 가수분해 활성도를 이용하여 조사하였다. 스트렙토카이네이스가 과량인 조건에서 프라즈미노젠의 양 만큼 이 복합체가 생성됨을 알았고, 프라즈미노젠이 과량인 경우에는 생성된 프라즈민의 활성을 Soybean Trypsin Inhibitor 로 특이적으로 저해 할 수 있었고, 따라서 이 복합체는 정량적으로 형성됨을 알 수 있었다.
이렇게 형성된 복합체의 synthetic ester 와 macromolecules 에 대한 특이성을 조사했는데, 결합을 위한 성질로서, (+) 전하를 띠는 것과 소수성을 갖는 부분이 둘 다 필요함을 보았고, macromolecules 에 대한 특이성도 나타났다. 이 복합체는 혈액 응고에 관여되는 피브리노젠이 존재할 때 활성이 상당히 증가하였고, inhibition 연구와 chemical modification 연구로 부터 imidazole 과 carboxyl group 이 그 복합체의 활성 부위에 관여한다고 생각된다.
