产谷氨酸脱羧酶片球菌的鉴定及其酶学性质

Identification and Enzymological Characterization of Glutamate Carboxylase-producing Pediococcus

从发酵蔬菜中分离一株产谷氨酸脱羧酶(glutamate decarboxylase,GAD)的乳酸菌HS2,其菌体细胞转化Glu1h,转化液中γ-氨基丁酸含量可达(3.114±0.133)g/L,通过形态培养特征、生理生化特征、16S rDNA序列比对及系统发育分析,鉴定菌株HS2是戊糖片球菌(Pediococcus pentosaceus)。菌株HS2GAD最适作用温度为35℃,最适作用pH4.5。酶的热稳定较好,在pH4.0～6.5于50℃处理4h,酶活基本稳定。Ca2+对酶有激活作用,5mmol/L和50mmol/L Ca2+浓度使酶活分别提高了37.21%和23.02%。Mg2+和Mn2+在50mmol/L浓度时激活作用明显,而Co2+在5mmol/L浓度激活作用较好。

A glutamate decarboxylase（GAD）-producing lactic acid bacteria（LAB） strain HS2 was isolated from pickled vegetable.When the biotransformation was conducted in cells with strain HS2 for 1 h,the content of γ-aminobutyric acid in biotransformation solution of strain HS2 was（13.114 ± 0.133） g/L.Base on morphological,physiological and biochemical characteristics,16S rDNA and phylogenic analysis,the strain HS2 was identified as Pediococcus pentosaceus.The optimal temperature and pH for GAD activity were 35 ℃ and 4.5.The GAD from strain HS2 was stable at 50 ℃ for 4 h and resistant to pH in the range of 4.0-6.5.In addition,calcium ions could result in a significant increase of GAD activity,which resulted in an enhancement of GAD activity by 37.21% and 23.02% at the concentrations of 5 mmol/L and 50 mmol/L Ca2＋.Similarly,Mg2＋ and Mn2＋ also could increase GAD activity at the concentration of 50 mmol/L,whereas Co2＋ could improve GAD activity at the concentration of 5 mmol/L.