Leytus S P, Bowles L K, Konisky J, Mangel W F
Proc Natl Acad Sci U S A. 1981 Mar;78(3):1485-9. doi: 10.1073/pnas.78.3.1485.
Preparations of outer membrane of two strains of Escherichia coli contain a protease that can activate the serum zymogen plasminogen to the active protease plasmin. The amount of plasmin formed is proportional to the membrane concentration. The kinetics of plasminogen activation are linear and obey the Michaelis--Menten rate equation. The Km(app) for the activation of dog plasminogen by E. coli outer membrane preparations is similar to the Km(app) for the activation of dog plasminogen by human urokinase. The E. coli enzyme is active in a membrane-associated form, as opposed to a secreted or soluble form, and is most likely a serine protease because it is inhibited by diisopropyl fluorophosphate. It is also inhibited from activating plasminogen by p-nitrophenyl-p-guanidinobenzoate and aprotinin. Analysis of the activation of plasminogen by the E. coli enzyme by NaDodSO4/polyacrylamide gel electrophoresis showed that the cleavage of plasminogen to plasmin was as specific as that exhibited in the activation of plasminogen to plasmin by urokinase. Possible in vivo roles for this plasminogen activator in E. coli outer membranes are discussed.
两株大肠杆菌外膜制剂含有一种蛋白酶，它能将血清酶原纤溶酶原激活为活性蛋白酶纤溶酶。形成的纤溶酶量与膜浓度成正比。纤溶酶原激活的动力学呈线性，符合米氏速率方程。大肠杆菌外膜制剂激活犬纤溶酶原的表观米氏常数（Km(app)）与人尿激酶激活犬纤溶酶原的表观米氏常数相似。大肠杆菌酶以膜结合形式具有活性，而非分泌或可溶形式，并且很可能是一种丝氨酸蛋白酶，因为它被二异丙基氟磷酸酯抑制。它也被对硝基苯基 - p - 胍基苯甲酸酯和抑肽酶抑制激活纤溶酶原。通过十二烷基硫酸钠/聚丙烯酰胺凝胶电泳分析大肠杆菌酶对纤溶酶原的激活表明，纤溶酶原裂解为纤溶酶与尿激酶激活纤溶酶原时一样具有特异性。讨论了这种纤溶酶原激活剂在大肠杆菌外膜中可能的体内作用。
