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Plasminogen-activator in human early milk: its partial purification and characterization
Thrombosis and Haemostasis
|April 30, 1981
Summary
Researchers purified a novel milk plasminogen activator from human transitional milk. This milk-activator is distinct from urokinase, showing unique properties and potential therapeutic applications.
Area of Science:
- Biochemistry
- Molecular Biology
- Human Physiology
Background:
- Human transitional milk contains various bioactive components crucial for infant development.
- Plasminogen activators play a role in fibrinolysis and tissue remodeling.
- Understanding the specific activators present in milk is important for nutritional and medical research.
Purpose of the Study:
- To isolate and characterize a plasminogen activator from human transitional milk.
- To determine if this milk-derived activator is biochemically similar to known activators like urokinase.
Main Methods:
- Partial purification of milk plasminogen activator using a multi-step procedure including chloroform treatment, ammonium sulfate precipitation, and sequential column chromatography (Sephadex G-150, CM Sephadex C-50, DEAE Sephadex A-50).
- Analysis of purified activator using polyacrylamide gel electrophoresis (PAGE) to assess purity and activity.
- Enzymatic assays to determine kinetic properties and inhibition patterns (e.g., hydrolysis of acetyl-glycyl-L-lysine methyl ester, inhibition by diisopropylfluorophosphate).
- Estimation of molecular weight by gel filtration and isoelectric points by gel isoelectric focusing.
- Immunological comparison using anti-urokinase globulin.
Main Results:
- A milk plasminogen activator was purified with a 2,400-fold increase in specific activity.
- PAGE revealed a single activity band, indicating a homogeneous preparation.
- The activator demonstrated kinetic properties similar to urokinase but was not inhibited by anti-urokinase globulin.
- Estimated molecular weight was approximately 86,000 Da, with isoelectric points at pH 7.2, 6.9, and 6.6.
Conclusions:
- Human transitional milk contains a distinct plasminogen activator.
- This milk-activator is biochemically and immunologically different from urokinase.
- The findings suggest a unique role for this activator in the milk environment or infant physiology.