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A fluorescence-based assay for human type II phospholipase A2
S G Blanchard1, C O Harris, D J Parks
1Department of Biochemistry, Glaxo Research Institute, Research Triangle Park, North Carolina 27709.
Analytical Biochemistry
|November 1, 1994
Summary
A new fluorescence assay accurately quantifies human Type II Phospholipase A2 (hPLA2-II) activity. This sensitive method enables efficient enzyme activity measurement without product separation, ideal for kinetic studies and high-throughput screening.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Human Type II Phospholipase A2 (hPLA2-II) plays a role in inflammatory diseases.
- Accurate and efficient quantification of hPLA2-II activity is crucial for research and drug discovery.
- Existing assays, such as radiochemical methods, have limitations in terms of continuous monitoring and product separation.
Purpose of the Study:
- To develop and validate a novel, continuous fluorescence-based assay for quantifying human Type II Phospholipase A2 activity.
- To compare the performance of the new assay with existing methods.
- To assess the suitability of the assay for kinetic analysis and high-throughput screening.
Main Methods:
- A specific fluorogenic substrate, 1-Acyl-2-(N-4-nitrobenzo-2-oxo-1,3-diazole)aminododecanoyl Phosphatidylethanolamine, was synthesized and prepared as a sonicated dispersion.
- Enzyme activity was measured by monitoring the increase in fluorescence intensity upon substrate hydrolysis.
- Kinetic parameters, including Km, were determined by fitting initial rate data to the Michaelis-Menten equation.
Main Results:
- The fluorescence intensity increase was directly proportional to hPLA2-II enzyme activity.
- The assay demonstrated high sensitivity and a Michaelis constant (Km) of 13 µM.
- The assay allowed for continuous measurement of enzyme activity without the need for substrate-product separation.
- Hydrolysis of a corresponding phosphatidylcholine substrate was significantly slower, indicating substrate specificity.
Conclusions:
- The developed fluorescence assay provides a sensitive, continuous, and efficient method for quantifying human Type II Phospholipase A2 activity.
- This assay is suitable for both detailed kinetic studies and large-scale screening applications, including automated plate readers.
- Advantages include high sensitivity and the use of a commercially available substrate, making it a valuable tool in biochemical and pharmacological research.