A vote for robustness: Monitoring serum enzyme activity by thin-layer chromatography of dabsylated bradykinin products

High-end analytical methods provide excellent data but may lack the robustness required in large analytical studies. In particular complex chemical matrices may cause difficulties and increase the need for extensive sample preparation. For screening of patients we thus developed a low-tech assay to monitor bradykinin degradation by serum proteases. The bradykinin concentration mirrors the activity of angiotensin-converting enzyme (ACE). Dabsylated bradykinin (DBK) and its labeled fragments DBK1-8 and DBK1-5 were visualized by thin-layer chromatography using only 3 μL of serum. Lower DBK1-5 levels indicated reduced ACE activity due to medication (ACE-inhibitors) or disease. Provided that purified DBK is available, the assay protocol itself is very simple and does not require any expensive high-end equipment.