Related Experiment Videos
Singlet oxygen ((1)O2) inactivates plasmatic free and complexed alpha2-macroglobulin
T W Stief1, J Kropf, V Kretschmer
1Institute of Clinical Chemistry and Molecular Diagnostics, Philipps-University, Marburg, Germany. thstief@post.med.uni-marburg.de
Thrombosis Research
|July 19, 2000
Summary
Oxidants like singlet oxygen inactivate alpha2-macroglobulin (alpha2M), a key human proteinase inhibitor. Even when bound to proteases, alpha2M is susceptible to oxidation, releasing active proteases and potentially increasing inflammation.
Area of Science:
- Biochemistry
- Immunology
- Protease Inhibitor Research
Background:
- Alpha2-macroglobulin (alpha2M) is a major human plasma proteinase inhibitor.
- Activated phagocytes produce oxidants like singlet oxygen ((1)O2).
- These oxidants inactivate specific serine protease inhibitors in human blood.
Purpose of the Study:
- To investigate the effect of nonradical oxidants, specifically singlet oxygen, on plasmatic alpha2-macroglobulin (alpha2M).
- To determine if alpha2M, when complexed with serine proteases, retains its resistance to oxidative inactivation.
- To identify the nature of the oxidant responsible for alpha2M inactivation and its potential targets.
Main Methods:
- Exposure of purified human plasma alpha2M to various oxidants, including chloramines and hydrogen peroxide.
- Testing the susceptibility of serine protease-alpha2M complexes to oxidative inactivation.
- Utilizing specific inhibitors of singlet oxygen and oxy-radical scavengers to elucidate the oxidant's nature.
Main Results:
- Plasmatic alpha2M is inactivated by nonradical oxidants, with an effective dose similar to alpha2-antiplasmin.
- Chloramines are significantly more potent inactivators of alpha2M than hydrogen peroxide.
- Unlike other inhibitors, alpha2M, even when bound to serine proteases, is sensitive to oxidation, leading to protease release.
- Inactivation is mediated by a nonradical oxidant with characteristics of singlet oxygen ((1)O2), targeting methionines or the thiol-ester.
Conclusions:
- Alpha2-macroglobulin (alpha2M) is susceptible to oxidative inactivation by singlet oxygen ((1)O2), even when complexed with proteases.
- Oxidative inactivation of alpha2M leads to the release of active proteases, potentially contributing to uncontrolled protease activity in inflammatory environments.
- This finding highlights a novel mechanism where alpha2M can act as a protease carrier, with implications for inflammation and thrombolysis.