反胶束体系中青霉素酰化酶活性及稳定性研究

Activity and Stability of Penicillin Acylase in Reversed Micelles

反胶束体系是一种新型的酶反应介质体系。构建合适的反应体系,使青霉素酰化酶在该体系中保持较高的酶活性,是实现反胶束体系中酶法合成头孢类抗生素的关键所在。本文分别考察了青霉素酰化酶在CTAB/正己醇和CTAB/异辛烷/正己醇两种反胶束体系中不同水含量和pH值对酶活力的影响。结果表明:包埋于CTAB/异辛烷/正己醇反胶束体系中的青霉素酰化酶在W0为14、pH为7.2时表现出较高的酶活性。试验中还考察了不同温度对包埋于CTAB/异辛烷/正己醇反胶束体系中的青霉素酰化酶活力的影响,并与游离酶液进行了比较。该酶在所采用的反胶束体系中的最适水解反应温度为39℃,较游离酶液的最适水解温度升高了2℃。同时酶的热稳定性亦较游离酶液有所提高,表现在CTAB/异辛烷/正己醇反胶束体系中,经50℃保温240 min,酶活保留率为76.0%, 而在同样条件下游离酶液仅为36.5%。

Reversed micelle is a novel reaction system for enzyme reaction. The key to the enzymatic synthesis of cephalosporin is the selection of a suitable reversed micelle system, in which the activity of penicillin acylase ought to be high. In this paper, the effects of water content, pH value on enzyme activity entrapped in cetyltrimethylammonium bromide (CTAB)/n-hexenol or CTAB/ isooctane/n-hexenol reversed micelles were investigated, respectively. The optimum conditions for enzyme activity in CTAB/ isooctane/n-hexenol reversed micelles were W0=14 and pH7.2, respectively. The effect of temperature on the enzyme activity entrapped in CTAB/ isooctane/n-hexenol reversed micelles was also investigated and compared to free enzyme solution. It was found that optimum temperature of enzyme for catalyzing the hydrolysis of penicillin G was 39℃, an increase of 2℃ over that of free enzyme solution. The thermostability of enzyme in reversed micelles was also improved. After being incubated at 50℃ for 240 min, the residual activity was 76.0% for the enzyme entrapped in CTAB/isooctane/n-hexenol reversed micelles, however, it was only 36.5% for the free enzyme solution incubated under the same conditions.