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Lung lymph capillary injury-related protease
1Department of Pharmacology, Mount Sinai School of Medicine, City University of New York, New York 10029.
The American Journal of Physiology
|October 1, 1989
Summary
A novel serine protease appears in sheep lung lymph following capillary injury. This trypsin-like enzyme, isolated and characterized, shows specific substrate cleavage, distinct from known proteases.
Area of Science:
- Biochemistry
- Physiology
- Enzymology
Background:
- Capillary damage in sheep, induced by endotoxin, oleic acid, or air emboli, leads to the release of a protease into lung lymph.
- The enzyme exhibits trypsin-like activity and its presence correlates with the severity of capillary injury.
Purpose of the Study:
- To isolate and characterize the serine protease appearing in lung lymph after capillary damage.
- To investigate the enzyme's substrate specificity and inhibitory profile.
Main Methods:
- Purification of the enzyme from sheep lung lymph using a multi-step affinity chromatography process (Reactive Blue-agarose, aprotinin-agarose, p-amino-benzamidine-agarose).
- Determination of molecular mass and subunit composition (two polypeptide chains linked by disulfide bonds).
- Enzyme activity assays using synthetic peptide and thioester substrates to determine specificity and identify key interactions.
Main Results:
- A serine protease (70-75 kDa) with trypsin-like activity was purified 9,000-fold.
- The enzyme preferentially cleaves substrates with multiple basic amino acids, indicating specific secondary interactions.
- Its inhibition profile and substrate specificity differentiate it from clotting, complement, and other known proteases.
Conclusions:
- A novel serine protease is associated with capillary injury in sheep lungs.
- The enzyme's unique characteristics suggest a potentially distinct physiological role.
- Further research is needed to elucidate the enzyme's origin and function in capillary damage.