海藻酸钠固定化S-腺苷甲硫氨酸合成酶的制备及其性质研究

研究了以海藻酸钠包埋法制备固定化S-腺苷甲硫氨酸（sAM）合成酶的条件，并考察了固定化酶的酶学性质。结果表明，最适固定化条件为：海藻酸钠质量分数3％、CaCl2质量分数4％、SAM合成酶加量（以每克海藻酸钠计）75mg、固定化时问30min，在此条件下，固定化酶活力回收率达到42％。固定化酶热稳定性较好，在50℃下保温5h仍保留69％的酶活力，而游离酶则完全失活；固定化酶在碱性条件下的稳定性较好，在pH值7．5～9．0的缓冲溶液中4℃下保温10h仍保留84％以上的酶活力；将固定化酶用于SAM的合成，连续反应5批次后，仍保留82％的酶活力。

Preparation and Properties of Sodium Alginate-Immobilized S-Adenosylmethionine Synthetase

The immobilization of S-adenosylmethionine（SAM） synthetase by embedding in sodium alginate was studied and properties of the immobilized enzyme were investigated. The results showed the optimal immo- bilization conditions were as follows：mass fraction of sodium alginate was 3 % ,mass fraction of calcium chloride was 4%,SAM synthetase amount was 75 mg,immobilization time was 30 rain. Under the optimum conditions, the activity recovery rate of the immobilized enzyme reached 42M. The immobilized enzyme showed a good ther- mal stability compared with the free enzyme. After incubated at 50 ＊C for 5 h,the immobilized enzyme main- tained 69 % of the original activity while the free enzyme lost all. The immobilized enzyme showed a good stabil- ity in alkaline solution,it still kept more than 84 - of the original activity when incubated in the buffer solution with pH value of 7. 5-9.0 at 4 ℃ for 10 h. When employed to synthesize SAM,the immobilized enzyme main- tained 82 % of the original activity after consecutive use for 5 times.