产γ-氨基丁酸屎肠球菌的鉴定及其谷氨酸脱羧酶酶学性质

Identification of γ-aminobutyric Acid producing Enterococcus faecium and Characterization of Its Glutamate Decarboxylase

目的:鉴定1株产γ氨基丁酸(γ-aminobutyric acid,GABA)的乳酸菌HS3,并研究了其谷氨酸脱羧酶(Glutamate decarboxylase,GAD)粗酶酶学性质。方法:根据形态培养特征、生理生化特征和16S rDNA序列比对及系统发育分析对菌株HS3进行了鉴定。采用菌体细胞破碎后的粗酶液,研究了温度、pH和金属离子对酶活的影响。结果:菌株HS3的形态培养和生理生化特征符合肠球菌属(Enterococcus)特征,其16S rDNA序列与Enterococcus faecium(EU717962)16S rDNA序列同源性达99%,鉴定菌株HS3为屎肠球菌(Enterococcus faecium),菌株HS3 GAD最适作用温度为40℃,最适作用pH4.5。酶的热稳定较好,50℃处理4h,在pH3.5～6.0酶活基本稳定。Ca2+对酶有激活作用,5mmol/L和50mmol/L浓度酶活分别提高了37.41%和17.43%。Ba2+和Zn2+在5mmol/L浓度时激活作用明显,而Mg2+在5mmol/L浓度激活作用较好。结论:菌株HS3的GAD活力较高,稳定性较好,为生物合成GABA提供了新的微生物菌种资源。

Objective：A lactic acid bacterium （LAB） for γ-amino butyric acid （GABA） production was identified. The characterization of its glutamate decarboxylase （GAD） was also reported in this paper. Method ： The strain HS3 was identified base on morphological, physiological and biochemical characteristics, 16S rDNA and phylogenic analysis. The characterization of its GAD was investigated by using cell disruption fluid as crude GAD. Result： The morphological, physiological and biochemical characteristics of strain HS3 accorded with the characteristics of Enterococcus. The similarity of the 16S rDNA sequences between strain HS3 and Enterococcus faecium （EU717962） was up to 99%. The strain HS3 was identified as Enterococcus faecium. The optimal temperature and pH value for the GAD activity was 40 ℃ and pH 4.5 respectively. The GAD from strain HS3 was stable under 50℃ for 4b and at pH 4.0 -6.5. 5mmol/L and 50mmol/L of Ca^2＋ significandy increased GAD activity, which promoted 37.41% and 7.43% of the GAD activity respectively. The activation were also observed on the concentration of 5mmol/L of Ba^2 ＋ , 5mmol/L of Zn^2＋ and 50mmol/L of Mg^2＋, respectively. Conclusion： The high activity and stable GAD from strain HS3 accounts for the new strain resources of GABA biosynthesis by LAB.