Sensitive colorimetric assay for angiotensin converting enzyme in serum

Area of Science:

• Biochemistry
• Clinical Chemistry
• Enzyme Assays

Background:

• Angiotensin converting enzyme (ACE) plays a crucial role in cardiovascular regulation.
• Accurate measurement of serum ACE activity is important for diagnosing and monitoring various conditions, including sarcoidosis.
• Existing methods for ACE assay may be complex or require specialized equipment.

Purpose of the Study:

• To develop and validate a sensitive and reliable colorimetric method for quantifying serum ACE activity.
• To establish the performance characteristics of the new assay, including its linear range and detection limit.
• To compare the proposed method with existing techniques and assess its applicability in clinical settings.

Main Methods:

• Serum samples were incubated with hippuryl-glycyl-glycine.
• Folin-Wu deproteinization was performed to isolate liberated glycyl-glycine.
• Glycyl-glycine was derivatized with trinitrobenzenesulfonate and absorbance measured at 420 nm.

Main Results:

• The colorimetric assay demonstrated a linear range exceeding 900 U/L and a detection limit below 4 U/L.
• Mean serum ACE activity was 281 U/L in healthy donors and 693 U/L in sarcoidosis patients.
• The method showed excellent precision (CVs < 2.8%) and strong correlation (r = 0.99) with HPLC.

Conclusions:

• A sensitive, precise, and widely applicable colorimetric assay for serum ACE has been developed.
• This method utilizes commonly available apparatus, making it suitable for routine clinical laboratories.
• The assay provides reliable results comparable to established methods, aiding in the diagnosis and management of ACE-related conditions.