The study was carried out to obtain angiotensin converting enzyme (ACE) with high specific activity and to evaluate the ability to maintain enzyme activity in extract products as well as in rabbit lungs using frozen condition. In the scope of the content, the study conducted an evaluation to select the appropriate extraction solvent of four solvents including acetone, ethanol, Tris-HCl and distilled water. Initially, the research results have helped determine distilled water as the suitable extraction solvent and the difference is not statistically significant compared to Tris-HCl solvent. Angiotensin converting enzyme extract that was obtained by distilled water solvent has a specific activity of 10.35 U/g
protein. In addition, the study investigated the ability to maintain angiotensin converting enzyme activity in rabbit lung and crude enzyme product during frozen storage (-18±2°C). The results of the study showed that angiotensin converting enzyme activity could be maintained for 3 months in rabbit lungs and 4 months in the crude product. Besides, the study also used ammonium sulfate with different concentrations to conduct angiotensin converting enzyme collection from extract product. The results of this content help determine the use of saturated ammonium sulfate with concentrations of 50% to 60% for the highest efficiency. The precipitation process helped obtain ACE products with a purity of 4.22 times, the specific activity of 42.64 U/g protein and the recovery rate of ACE up to 29.37%.