ISSN:
1440-1681
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
1. Somatic angiotensin I-converting enzyme (ACE) is a protein that contains two similar domains (N- and C-terminal), each possessing an active site. We have examined the effects of a generator of hydroxyl radicals (g•OH: 2,2′-azo-bis(2-amidinopropane)) and hydrogen peroxide (H2O2) on ACE using an in vitro approach.2. The generator of hydroxyl radicals inactivated ACE in a time (2–6 h)- and concentration (0.3–3 mmol/L)-dependent manner at 37°C. When ACE was coincubated for 4 h with g•OH (3 mmol/L), its activity decreased by 70%. Addition of dimethylthiourea or mannitol + methionine, two •OH scavengers, resulted in a significant protection of ACE activity. Mercaptoethanol and dithiotreitol, two thiol-reducing agents, also efficiently protected ACE activity.3. The hydrolysis of two natural and domain-specific substrates was explored. The hydrolysis of angiotensin I, preferentially cleaved by the C-domain, was significantly inhibited (57–58%) after 4 h exposure to g•OH (0.3–1 mmol/L). Under the same conditions of exposure, the hydrolysis of N-acetyl-Ser-Asp-Lys-Pro, a specific substrate for the N-domain, was only slightly inhibited by 1 mmol/L g•OH.4. Hydrogen peroxide, another source of •OH, was used. After exposure to H2O2 (3 mmol/L; 4 h), an 89% decrease in ACE activity was observed. Pretreatment with the iron chelator deferoxamine (1 mmol/L) attenuated H2O2-mediated ACE inactivation, demonstrating that the effect of H2O2 was partly due to its conversion into •OH (Fenton reaction).5. In summary, our findings demonstrate that g•OH and H2O2 inhibit ACE activity and suggest a preferential action of g•OH on the C-domain of the enzyme.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1440-1681.2001.03419.x
