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Macromolecular chromogenic substrates for measuring proteinase activity
G L Hortin1, I Warshawsky, M Laude-Sharp
1Clinical Pathology Department, National Institutes of Health, Bldg. 10, Room 2C-407, 10 Center Dr., Bethesda, MD 20892-1508, USA. ghortin@cc.nih.gov
Clinical Chemistry
|February 13, 2001
Summary
Novel macromolecular substrates (macrosubstrates) offer improved measurement of proteinase activity, especially for sterically hindered enzymes like alpha(2)-macroglobulin-proteinase complexes, enabling more accurate functional assays.
Area of Science:
- Biochemistry
- Enzymology
- Proteomics
Background:
- Proteinase activity assays commonly use small chromogenic substrates, which may not accurately reflect physiological conditions.
- This limitation can lead to inaccurate measurements of enzyme activity, particularly for larger or complexed proteinases.
Purpose of the Study:
- To develop and characterize macromolecular substrates (macrosubstrates) for more accurate proteinase activity measurement.
- To assess the utility of macrosubstrates for evaluating sterically hindered proteinase complexes.
Main Methods:
- Macrosubstrates were synthesized by linking small chromogenic substrates to polyethylene glycol.
- Hydrodynamic size was determined using gel filtration.
- Enzyme activity was measured spectrophotometrically for free proteinases and alpha(2)-macroglobulin-proteinase complexes.
Main Results:
- Macrosubstrates exhibited hydrodynamic radii similar to proteins of 18,000 molecular weight.
- Various macrosubstrates efficiently cleaved by chymotrypsin, trypsin, and thrombin.
- Macrosubstrate efficiency varied, with activity changes ranging from a 60% decrease to a 30-fold increase.
- Proteinases complexed with alpha(2)-macroglobulin showed approximately 10-fold lower activity with macrosubstrates compared to small substrates.
Conclusions:
- Macrosubstrates serve as effective substrates for measuring proteinase activity, including sterically hindered molecules.
- These findings suggest macrosubstrates can enhance the accuracy of functional assays for proteinases, such as coagulation factors.