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Production of the modified form of human plasminogen by alpha 2-macroglobulin-plasmin complexes
Abstract:
It has been speculated that the modified form of plasminogen, a precursor of proteolytic enzyme plasmin in plasma, plays an important role in fibrinolysis in the blood. The present study was undertaken to examine the production by alpha 2-macroglobulin-plasmin complexes. alpha 2-Macroglobulin-plasmin complexes were purified from urokinase-activated plasma by affinity chromatography on lysine-Sepharose and gel filtration on Ultrogel AcA 22. The plasmin complex converted native plasminogen into the modified form more easily in the presence of epsilon-aminocaproic acid. The modification of native plasminogen by alpha 2-macroglobulin-bound plasmin was completely inhibited by aprotinin, and partly by soybean trypsin inhibitor. alpha 2-macroglobulin-bound plasmin produced modified plasminogen in human plasma where potent plasmin inhibitors exist, though the degree of production was small. The present results support the speculation of the important role of the modified form in vivo.
Insights
Modified plasminogen, a key player in blood clot breakdown (fibrinolysis), is produced by alpha 2-macroglobulin-plasmin complexes. This supports its important role in the body.
Area of Science:
- Biochemistry
- Hematology
- Proteolysis
Background:
- The modified form of plasminogen is speculated to be crucial for fibrinolysis.
- Plasminogen is a precursor to the proteolytic enzyme plasmin found in plasma.
Purpose of the Study:
- To investigate the production of modified plasminogen by alpha 2-macroglobulin-plasmin complexes.
- To understand the role of these complexes in plasminogen modification.
Main Methods:
- Purification of alpha 2-macroglobulin-plasmin complexes from urokinase-activated plasma using affinity chromatography (lysine-Sepharose) and gel filtration (Ultrogel AcA 22).
- Assessing the conversion of native plasminogen to its modified form in the presence of epsilon-aminocaproic acid.
- Evaluating the inhibitory effects of aprotinin and soybean trypsin inhibitor on plasminogen modification.
Main Results:
- Alpha 2-macroglobulin-bound plasmin efficiently converted native plasminogen into the modified form, especially with epsilon-aminocaproic acid.
- Aprotinin completely inhibited this modification, while soybean trypsin inhibitor partially inhibited it.
- Modified plasminogen was produced in human plasma, despite the presence of plasmin inhibitors, albeit to a lesser extent.
Conclusions:
- The study supports the hypothesis that the modified form of plasminogen plays a significant role in in vivo fibrinolysis.
- Alpha 2-macroglobulin-plasmin complexes are capable of producing modified plasminogen in a plasma environment.