明胶膜固定化脲酶的制备及性质

以明胶为载体,戊二醛为交联剂,采用包埋-交联联用法制备了明胶膜固定化脲酶,其酶活力为6 07U/g载体,酶活力收率为66 1%。最优固定化条件是包酶量为10mg酶/g明胶,ρ(明胶)=100g/L,φ(戊二醛)=0 5%。研究了固定化酶的性质,并与游离酶作了比较,游离酶的最适pH=7 0,固定化酶的最适pH=6 5;游离酶的最适温度为60℃,固定化酶的最适温度升至70℃;固定化酶与游离酶的米氏常数Km分别为11 7mM和12 4mM;固定化酶在80℃下180min仍保留初始活力的10%,而游离酶几乎完全失活。固定化酶重复使用20次其活力仅下降15%,4℃下贮存35d后仍保持初始活力的55%。

Preparation and Properties of Immobilized Urease in Gelatin Membrane

Urease was entraped in glutaraldehyde cross-linked gelatin membrane with activity of 6.07 U/g carrier and 66.1% retention of activity.The optimum conditions of immobilization were urease loading ratio 10 mg enzyme/g gelatin,ρ(gelatin)=100 g/L and φ(glutaraldehyde)=0 .5%.Properties of the immobilized urease were investigated and compared with the free enzyme.The optimum pH value was 7.0 and 6.5 for the free and the immobilized urease respectively.The optimum temperature was 60 ℃ for the free urease,while it shifted to 70 ℃ for the immobilized enzyme.Michaelis constant K_m was 11.7 mM and 12.4 mM for the immobilized urease and the free enzyme respectively.At 80 ℃ after 180 minutes,a complete loss of activity of the free enzyme was recorded while the immobilized urease retained 10% of its initial activity.The enzyme activity of the immobilized urease decreased by only 15% even after repeated use for 20 times,and the immobilized urease stored at 4 ℃ retained 55% of its initial activity even after 35 d.