CONCENTRATION-DEPENDENT EFFECTS OF ZINCON ANGIOTENSIN-CONVERTING ENZYME-2 ACTIVITY

Atrium

Objective. This study was conducted to ascertain the importance of zinc on angiotensin-converting enzyme-2 (ACE-2) activity. Background. ACE-2 degrades angiotensin II (Ang II) and forms Ang (1-7), which antagonizes much of the pathophysiology of Ang II. ACE-2, a member of the M2 family of metallopeptidases, contains a HEXXH motif that functions as the zinc binding domain at its active site. Methods. We measured metabolism of an artificial substrate of ACE-2 (MCA-APK[Dnp]) by rat kidney and lung, as well as recombinant human ACE-2 (rhACE-2), at 0, 10, 100, or 1000 μM zinc acetate; with or without the ACE-2 inhibitor MLN-4760. Metabolism of the fluorogenic substrate MCAAPK(Dnp) (50 μM) was measured at 393 nm with excitation at 328 nm at 37°C. Results. In both rat tissues and rhACE-2 the rate of MLN-4760-blockable metabolism of substrate was highest with no zinc or 10 μM zinc. However, in the presence of 100 μM zinc, activity was significantly (p < 0.05) decreased in rat lung and rhACE-2 compared to 0 or 10 μM zinc. In the presence of 1000 μM zinc, activity was further reduced (p < 0.05) in all three preparations compared to 0, 10 and 100 μM zinc. Conclusion. These results suggest that ACE- 2 may have additional lower affinity binding site(s) for zinc that interfere with its ability to metabolize its substrates. Assays of ACE-2 activity should not be run in the presence of zinc concentrations greater than 10 μM. Grants. This study was funded by NIH-NHLBI HL113905