含 gly A的基因工程菌所表达的 SHMT可催化甲醛和甘氨酸特异地合成 L-丝氨酸。对酶法合成的部分条件进行了优化 ,并根据甲醛滴定的原理 ,确定了通过检测 p H变化控制甲醛流加速度的方案 ,最终的反应液中 L-丝氨酸浓度达 0 .2 mol/L。反应结束后的酶反应液中同时含有甘氨酸和丝氨酸 ,利用国产 71 7树脂获得较为理想的分离效果 ,丝氨酸的收率达 77% ,高效液相分析表明其中不含甘氨酸等杂质 SHMT expressed by genetically engineered bacteria containing gly A catalyzes the specific synthesis of L-serine by formaldehyde and glycine. The conditions of the enzymatic synthesis were optimized. According to the principle of formaldehyde titration, the scheme of controlling the acceleration of formaldehyde flow by detecting the change of p H was determined. The concentration of L-serine in the final reaction solution was 0.2 mol / L. After the reaction, the enzyme reaction solution contained both glycine and serine, and the best separation effect was obtained with domestic 71 7 resin. The yield of serine was 77%. The HPLC analysis showed that there was no glycine and other impurities