[Immobilization and properties of angiotensin converting enzyme].

OBJECTIVE

To study the immobilization of angiotensin converting enzyme (ACE) for purifying ACE inhibitor from a native peptide mixture.

METHODS

The experiment was carried out under the low water activity condition, using tosylate chloride activating side-chain hydroxyl group of Sepharose CL-4B agarose to form a high active group which could react with the free amino-group of ACE to link the enzyme with agarose.

RESULTS

Immobilized ACE not only had a wider pH range, but also had a 0.6 unit right-move optimum pH than soluble ACE. After treated in pH9.0 and pH 6.5 conditions for 24 h respectively, 82% and 68% enzyme activities of immobilized ACE was maintained, and soluble ACE remained 64% and 39%. Immobilized and soluble ACE both appeared maximum enzyme activity at about 50 degrees C, the soluble ACE would lose almost all its activity when temperature kept rising. When kept at 40 degrees C and 50 degrees C for 2 h, the activity of immobilized ACE remained 82% and 34% respectively, while the soluble ACE remained 52% and completely inactivated. After two kinds of enzymes were stored at 20 degrees C for one month, immobilized ACE remained 61% activity, as compared with the 20% activity residual of soluble ACE.

CONCLUSION

The immobilized ACE had a better stability than soluble ACE in conditioned pH and temperature.