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用不同酸酐对木瓜蛋白酶进行化学修饰,以三硝基苯磺酸法(TNBS)测定修饰酶的平均氨基修饰度,对修饰前后的木瓜蛋白酶分别纯化并通过UV-vis和IR对其结构进行了表征.考察了温度、pH值和表面活性剂SDS对化学修饰的木瓜蛋白酶活力的影响,并与天然木瓜蛋白酶进行了比较,对天然酶和修饰酶进行了动力学研究.结果表明,化学修饰木瓜蛋白酶的最适反应温度为80℃;最适pH值为9.0;在SDS浓度为5mg·mL-1时修饰酶酶活仍能保持在50%左右;在所有酶中,均苯四甲酸酐修饰木瓜蛋白酶的催化效率最高,为2.442×102.与天然木瓜蛋白酶相比,化学修饰木瓜蛋白酶的热稳定性、耐碱性和耐洗涤性得到了显著提高.
The papain was chemically modified with different anhydrides. The average degree of amino group modification of the modified enzymes was determined by TNBS. The papains before and after the modification were separately purified and their structures were characterized by UV-vis and IR Characterization.The effects of temperature, pH value and surfactant SDS on the chemical modification of papain were investigated and compared with that of natural papain.The kinetics of natural enzyme and modified enzyme were studied.The results showed that the chemical modification of papaya The optimal reaction temperature of protease was 80 ℃; the optimum pH was 9.0; the enzyme activity was still about 50% at SDS concentration of 5 mg · mL-1; in all enzymes, the pyromellitic anhydride The highest catalytic efficiency of papain was 2.442 × 102. Compared with natural papain, the chemical stability, heat resistance, alkali resistance and washing resistance of papain were significantly improved.