Abstract: Cross-linked angiotensin converting enzyme aggregates(ACE-CLEAs) were prepared and their characteristics were compared with that of free ACE including optimal temperature and pH, Km, vmax, thermal and pH stabilities. Based on the relative activity of immobilized enzyme, the optimal preparation conditions should be as follows:precipitating the enzyme with 80% saturated ammonium sulfate for 0.5 h, and then cross-linking it with 0.02%(mass fraction) glutaraldehyde for 1 h. According to the comparison for enzymology property, ACE-CLEAs had better thermal and pH stabilities than free ACE, and the Km of ACE-CLEAs was close to that of free ACE, suggesting that ACE-CLEAs had an almost equal affinity to enzyme as the free ACE.

Key words: Angiotensin Converting Enzyme, Cross-linked Enzyme Aggregates, Immobilization