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A continuous fluorescence assay of renin activity
G T Wang1, C C Chung, T F Holzman
1Pharmaceutical Product Division, Abbott Laboratories, Abbott Park, Illinois 60064.
Analytical Biochemistry
|May 1, 1993
Summary
A new fluorogenic peptide substrate enables sensitive, continuous measurement of human renin activity. This assay detects low renin levels with high accuracy, offering a valuable tool for research and diagnostics.
Area of Science:
- Biochemistry
- Enzymology
- Assay Development
Background:
- Human renin is a key enzyme in the renin-angiotensin-aldosterone system, regulating blood pressure.
- Accurate measurement of renin activity is crucial for understanding and treating cardiovascular diseases.
- Existing assays may lack the sensitivity or continuous monitoring capabilities required for certain applications.
Purpose of the Study:
- To develop a novel fluorogenic peptide substrate for the continuous and sensitive measurement of human renin proteolytic activity.
- To characterize the kinetic properties of the developed substrate in renin-catalyzed reactions.
- To establish the sensitivity and applicability of the assay in detecting low levels of human renin.
Main Methods:
- Synthesis of a novel fluorogenic peptide substrate (DABCYL-gaba-Ile-His-Pro-Phe-His-Leu-Val-Ile-His-Thr-EDANS) incorporating the human angiotensinogen cleavage site.
- Utilizing resonance energy transfer (FRET) for intramolecular fluorescence quenching in the intact substrate.
- Monitoring time-dependent increases in fluorescence intensity upon renin-mediated substrate cleavage.
- Kinetic analysis of renin-catalyzed hydrolysis and determination of Michaelis constant (Km).
- Enzyme dilution experiments to assess assay sensitivity.
Main Results:
- The fluorogenic substrate demonstrated efficient fluorescence quenching via FRET, with quenching dependent on the proximity of EDANS and DABCYL moieties.
- Renin cleavage occurred specifically at the Leu-Val bond, mirroring the angiotensinogen cleavage site.
- The assay exhibited a Km of approximately 1.5 microM at physiological pH, consistent with a simple substrate inhibition model.
- The continuous assay format demonstrated high sensitivity, detecting human renin as low as 30 ng/ml within 3-5 minutes.
Conclusions:
- A novel, sensitive, and continuous fluorescence assay for human renin activity has been successfully developed using a specifically designed fluorogenic peptide substrate.
- The assay accurately reflects renin's specific cleavage site and exhibits favorable kinetic properties.
- The high sensitivity and rapid detection capability make this assay a valuable tool for biochemical research and clinical diagnostics related to renin-dependent conditions.