Partial characterization of angiotensin I-converting enzyme of the aorta in rats

The angiotensin I-converting enzyme of rat aorta was solubilized with Triton X-100 and partially purified by chromatography with DEAE-cellulose and Sephadex G-200. The specific activity of the purified enzyme was 4.01 units/mg of protein. The enzyme was separated into 6 isozymes with different molecular weights of 460,000, 440,000, 260,000, 220,000, 217,000 and 119,000 by Sephadex G-200 gel filtration. All the isozymes migrated as a single band with a molecular weight of 112,000 on SDS/polyacrylamide gel electrophoresis. These isozymes showed the same optimal pH (8.3) and temperature (30 degrees C). Converting-enzyme, which might be produced in the arterial wall, may play a role in the local control of vascular tone through the conversion of angiotensin I into II in vascular tissue.