Purification and Characterization of Porcine Angiotensin Converting Enzyme 2

Angiotensin converting enzyme 2 (ACE2) is one of the key enzymes involved in blood pressure regulation. Conventional purification method for ACE2 was complicated and with low efficacy. Thus, it is necessary to optimize the purification method to provide reference for the research of ACE2. In this study, porcine kidney was used as raw material, and ACE2 was purified by acid precipitation, ammonium sulfate precipitation, column chromatographies of DEAE-Sepharose, Q-Sepharose and Phenyl Sepharose. The effects of temperature, pH, metal ions, and inhibitors on the activity of ACE2 were explored, and PAS staining was adopted to verify whether it is glycoprotein or not. The results showed that the molecular weight of purified ACE2 was about 98 kDa, with purification folds of 149.8, and yield of 0.1%. Purified protein was identified by mass spectrometry, and 41 peptides were obtained which were identical to the amino acid sequence of porcine ACE2. ACE2 was a metalloproteinase, its optimum pH was 7.0 and optimum temperature was 40 ℃. Metal ion Zn²⁺ could activate its activity while Cu²⁺, Fe³⁺ and Cd²⁺ inhibited it. The results of circular dichroism spectrum showed that the denaturation temperature of ACE2 was 67.5 ℃, and its secondary structure irreversibly changed after heating. Porcine ACE2 was a glycoprotein as revealed by PAS staining. This study would provide a reference for effective purification of natural ACE2 and is also helpful to promote the development of functional foods targeting ACE2.