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A crosslinked tetrameric alpha 2M that binds but incompletely entraps trypsin
F H Khan1, M Mirza, M Saleemuddin
1Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, India.
Biochemistry and Molecular Biology International
|September 1, 1994
Summary
Researchers created a crosslinked alpha-2-macroglobulin preparation using glutaraldehyde. This modified inhibitor bound trypsin, but offered incomplete protection against soybean trypsin inhibition compared to the native form.
Area of Science:
- Biochemistry
- Proteomics
- Enzymology
Background:
- Alpha-2-macroglobulin (A2M) is a key plasma proteinase inhibitor.
- Understanding A2M's structural modifications and proteinase interactions is crucial for its function.
- Glutaraldehyde crosslinking is a method to stabilize protein structures.
Purpose of the Study:
- To characterize a glutaraldehyde-crosslinked preparation of human alpha-2-macroglobulin.
- To investigate the interaction of trypsin with crosslinked A2M.
- To assess the functional consequences of crosslinking on A2M's inhibitory activity.
Main Methods:
- Purification of human plasma alpha-2-macroglobulin.
- Crosslinking of A2M using glutaraldehyde at low temperature.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for molecular weight determination.
- Nondenaturing gel electrophoresis to assess electrophoretic mobility.
- Enzyme inhibition assays using trypsin and soybean trypsin inhibitor.
Main Results:
- A crosslinked A2M preparation was successfully obtained, migrating as a 780 KDa polypeptide in SDS-PAGE.
- Crosslinked A2M exhibited mobility similar to trypsinized native A2M under nondenaturing conditions.
- Trypsinization of crosslinked A2M increased its mobility and led to proteinase association.
- Trypsin bound to crosslinked A2M was incompletely protected from inhibition by soybean trypsin inhibitor.
Conclusions:
- Glutaraldehyde crosslinking yields a stable A2M preparation with altered electrophoretic properties.
- Crosslinked A2M can bind proteinases like trypsin.
- The crosslinking process affects A2M's ability to protect bound proteinases from other inhibitors.