血管紧张素转换酶的固相化与性质

目的为从天然肽类混合物中分离血管紧张素转换酶（ angiotensin converting enzyme, ACE）抑制活性物质,对固相化 ACE（固相酶）进行研究。方法在低水活度条件下利用苯甲磺酰氯活化 Sepharose CL- 4B凝胶侧链基团上的羟基,形成高反应活性的苯磺酰基团,通过与 ACE上的氨基反应将酶固定于琼脂糖凝胶。结果固相化 ACE的反应 pH范围较宽,最适反应 pH比溶液酶（自由酶）增加 0.6个单位,达到 8.8。分别在 pH9.0和 pH6.5条件下处理 24 h,固相酶活力保留 82％和 68％,溶液酶只剩下 64％和 39％。两种酶均在 50℃左右活力最大,温度继续升高溶液酶迅速失活。分别在 40℃和 50℃处理 2 h,固相酶剩余活力为 82％和 34％,溶液酶为 52％和完全失活。 20℃放置 1个月,固相酶剩余活力为 61％,而溶液酶只有 20％。结论 ACE固相酶在 pH和温度稳定性方面强于溶液酶。

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.