假单胞菌N-13中丝氨酸羟甲基转移酶的酶学性质研究

Study on the Properties of SHMT from Pseudomonas N-13

从产L-丝氨酸菌株假单胞菌N-13中纯化了丝氨酸羟甲基转移酶,并对其性质进行了研究。结果表明,丝氨酸羟甲基转移酶酶活力在pH=7.0～9.0间稳定,最适宜pH=8.0;酶的最适温度为35℃,在30～40℃水浴30 min酶活力未见明显下降。磷酸吡哆醛的最适添加浓度为25μmol·L-1。研究了不同金属离子对酶活力的影响,结果表明,Cu2+和Co2+可分别提高酶活力22%和10%;但Mn2+、Mg2+、Zn2+对酶活力有强烈的抑制作用,Ca2+对酶活力没有影响。L-丝氨酸产量与丝氨酸羟甲基转移酶是相互依存的关系,而且在产量越高的菌株中SHMT的活性越高。

SHMT of L-serine-producing strain of Pseudomonas N-13 was purified and characterized.The enzyme was stable between pH 7.0 and 9.0 with a optimum pH=8.0.The optimum temperature was 35℃,and no significant activity loss was observed when the enzyme was incubated at 30～40℃ for 30min.The optimal concentration of PLP was 25μmol·L-1.The effect of different metal ions on the activity of the enzyme were also investigated.Some metal ions,including Cu 2＋ and Co 2＋,could increase the enzyme activities by 22% and 10%,respectively,while some other metal ions,including Mn 2＋,Mg 2＋ and Zn 2＋,strongly inhibited the enzyme activity.The enzyme activity was not affected by Ca 2＋.The ability of accumulating L-serine in the mutants was relevant with SHMT activity,higher SHMT activity,more yield of L-serine.