A radioassay for angiotensin converting enzyme

Area of Science:

• Biochemistry
• Enzyme Assays
• Analytical Chemistry

Background:

• Current methods for measuring angiotensin converting enzyme (ACE) activity are complex and limit widespread use.
• Developing a simpler, more sensitive assay for ACE is crucial for broader clinical and research applications.

Purpose of the Study:

• To develop and validate a simple, sensitive, four-step radioassay for measuring angiotensin converting enzyme (ACE) activity.
• To compare the performance of the new radioassay with existing spectrophotometric and liquid chromatographic methods.

Main Methods:

• A novel four-step radioassay utilizing 14C-Hippurate-L-Histidyl-L-Leucine as a substrate.
• Measurement of the product, 14C-Hippurate, to determine ACE activity.
• Incubation at pH 7.0 (Hepes buffer) to optimize assay sensitivity.
• Split-sample comparison with spectrophotometric and liquid chromatographic methods.

Main Results:

• The radioassay demonstrated a 50% increase in sensitivity when incubated at pH 7.0 compared to pH 8.0.
• Good correlation (r=0.868) was observed between the radioassay and the spectrophotometric method in a split-sample study.
• No significant difference in results was found between the radioassay, spectrophotometric, and kinetic methods, though liquid chromatography yielded different results.

Conclusions:

• The developed radioassay offers enhanced technical ease and sensitivity for measuring ACE activity.
• This simplified assay has the potential to increase the general availability and application of ACE testing.
• The radioassay provides a reliable alternative to traditional methods, with optimized conditions improving performance.