海藻酸钠明胶协同固定S-腺苷甲硫氨酸合成酶

Research on the Immobilization of S-Adenosylmethionine Synthetase with Sodium Alginate-Gelatin

以海藻酸钠和明胶为载体,对S-腺苷甲硫氨酸合成酶进行固定化。再用戊二醛对其进一步交联,增强固定化酶的稳定性。考察了海藻酸钠和明胶质量分数、CaCl2质量分数、酶和载体比例以及交联剂戊二醛体积分数等因素对固定化酶的影响。结果表明,最佳固定化条件为:海藻酸钠质量分数2.0%、明胶质量分数1.0%、CaCl2质量分数4.0%、固定化酶量为2.5 g/L凝胶、戊二醛体积分数0.6%。交联固定化酶热稳定性得到大幅度提高,在50℃下保温5 h仍保留72%的活力,而游离酶则完全失活。交联固定化酶在碱性溶液中的稳定性较高,在pH=8.0～9.0的缓冲液中4℃保温10 h酶活性仍保留87%以上。将交联固定化酶用于S-腺苷甲硫氨酸的合成,连续反应8批次后酶活性仍保留65%。

S-Adenosylmethionine （SAM） synthetase was immobilized on sodium alginate-gelatin and then cross-linked with glutaraldehyde for improving the stability of the immobilized enzyme. The properties of the immobilized enzyme were identified. The results show that the optimal conditions for the immobilization of the enzyme were as follows：the mass fraction of sodium alginate, gelatin and calcium chloride was 2.0% , 1.0% and 4.0% respectively;the amount of enzyme was 2.5 g/L gel;the volume fraction of glutaraldehyde was O. 6%. The cross-linked immobilized enzyme showed good stability compared with the free enzyme. After incubation at 50 ℃ for 5 h, the immobilized enzyme maintained 72% of the original activity while the free enzyme lost all activity. The cross-linked immobilized enzyme showed good stability in alkaline solution. It still kept more than 87% of the original activity when incubated in the buffer of pH = 8.0 - 9.0 at 4 ℃for 10 h. The cross-linked immobilized enzyme was employed to synthesize the SAM and it retained 65 % activity after eight times repeated operations.