研究了玉米胚谷氨酸脱羧酶(GAD)的性质。结果表明:玉米胚GAD的最适温度为40℃,最适pH为5.7,其热稳定较差,60℃下保温1 h,酶活下降至39%,85℃时酶完全失活,而此酶在pH4.5～7.5可保持80%以上的酶活。玉米胚GAD对Glu的Km值和Vmax分别为51.87 mmol/L和1.807 mg/min。另外,KCl、NaCl和SDS对玉米胚GAD活性有较大的抑制作用,而Ca2+对此酶的活性有较强的激活作用,可提高底物与玉米胚GAD的亲和力。

The properties of glutamate decarboxylase(GAD) from corn germ were investigated.The GAD showed its maximal activity at 40℃ and pH5.7 respectively.The GAD was sensitive to temperature.Its activity remains 39% under 60 ℃ after 1h,and it is inactive at 85℃.However,the GAD had a relatively wide pH range for stability,whose activity remained at 80% under pH 4.5~7.5.The Km and Vmax of GAD for Glu were 51.87mmol/L and1.807mg/min respectively.Moreover,KCl,NaCl and SDS inhibited the GAD activity remarkably,whereas Ca2+ could activate the GAD,this showed that Ca2+ enhanced the affinity between enzyme and the substrate.