有序介孔TiO2固载g-谷氨酰转肽酶催化合成S-bzl-g-glutamyl-L-cysteine

以有序介孔TiO2(OM-TiO2)为载体对B. subtilis NX-2 GGT进行吸附固载. 圆二色光谱分析和活性位点滴定结果表明，固定化前后酶的二级结构和活性位点数变化很小，固定化后GGT对供体的亲和力及转肽反应催化常数均有不同程度下降，但固定化酶对产物的亲和力有明显提高. 固定化后GGT的热稳定性和pH稳定性均较游离酶有显著提高，固定化酶稳定性良好，经10批次转化后，固定化催化活性仍保持74%. 以固定化GGT为催化剂，在L-谷氨酰胺(L-Gln) 5 mmol/L、S-苄基-半胱氨酸(S-bzl-cys) 15 mmol/L、酶浓度0.062 U/mL和pH 9.0条件下，40℃水浴反应5 h，产物浓度为1.2 mmol/L.

Enzymatic Synthesis of S-bzl-g-Glutamyl-L-Cysteine with g-Glutamyltranspeptidase Immobilized onto Ordered Mesoporous TiO2

g-Glutamyltranspeptidase (GGT) was adsorbed from B. subtilis NX-2 onto ordered mesoporous TiO2 (OM-TiO2). The immobilized GGT was characterized with circular dichroism spectrum and active site titration method. The secondary structure and number of active sites of GGT were little affected after immobilization. The immobilized GGT appeared some decline in the affinity of GGT toward donor substrate and catalytic constants. However, the affinity of immobilized GGT toward S-bzl-GGC was much higher than that of free GGT. Thermal and pH stability of GGT were significantly increased via immobilization. Residual activity of immobilized GGT still exceeded 74% of its initial value after reusing for 10 batches. At the conditions of Gln 5 mmol/L, S-bzl-cys 15 mmol/L, immobilized GGT 0.062 U/mL and pH 9.0, a maximal product yield of 1.2 mmol/L was obtained after incubation at 40℃ for 5 h.