海洋来源褐藻胶裂解酶分离纯化及酶学性质研究
Purification and characterization of the alginate lyase isolated from marine

以假交替单胞菌（Pseudoalteromonas sp. zb7-4）发酵制备褐藻胶裂解酶粗酶液，采用弱阴离子DEAE交换层析分离褐藻胶裂解酶，分析纯化褐藻胶裂解酶AlgL的酶学特性. 结果表明：AlgL的表观分子质量约为32ku，比活力为（208.26±5.87）U·mg-1；其最适反应pH为7.0，在pH为6.0~10.0范围内稳定性较好，保温1h仍能保持80%以上的相对酶活力；最适反应温度50℃，在40℃保温30min，其残余酶活力高于80%；Cu2+、Cr3+、Co2+、Ba2+、Sr2+、Hg2+对该酶具有不同程度的抑制作用，Hg2+抑制作用最为明显；该酶具有较好的盐耐受性，在3mol·L-1 NaCl反应体系中保温2h，仍残余66%酶活力. 动力学参数Km、Vmax、Kcat测定表明，该酶对聚古罗糖醛酸钠(PG)亲和力较高，为偏好聚甘露糖醛酸钠(PM)裂解作用的双功能酶.
Alginate lyase AlgL was successfully purified from fermented broth of Pseudoalteromonas sp. zb7-4 by DEAE weak anion exchange chromatography and the enzymatic properties of alginate lyase were characterized. The results showed that the purified alginate lyase was a monomer with apparent molecular weight of approximately 32ku and specific activity of (208.26±5.87)U·mg-1. The optimum pH for enzyme was 7.0，it was stable in the pH range of 6.0 to 10.0，and its relative enzyme activity could still maintain more than 80% after 1 h’s incubation. The optimum temperature for enzyme was 50℃，and its residual enzyme activity was still 80% after 30 min’s incubation at 40℃. Cu2+，Cr3+，Co2+，Ba2+，Sr2+，Hg2+ showed inhibitory effects on the enzyme activity while Hg2+ was the most obvious. The enzyme had a good ability of salt tolerance，and its relative enzyme activity retained more than 66% after 2 h’s incubation in 3mol·L-1 NaCl. The values of Km、Vmax、Kcat showed that the enzyme was a bifunctional enzyme which prefered sodium polymannuronate (Poly M)