玉米胚谷氨酸脱羧酶的性质

Some Properties of Glutamate Decarboxylase from Corn Germ

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 pHi. 7 respectively. The GAD was sensitive to temperature. Its activity remains 39% under 60 ℃ after lh, and it is inactive at 85~C. However, the GAD had a relatively wide pit range tor stability, whose activity remained at 80% under pH 4.5 -7.5. The Km and V of GAD for Glu were 51.87mnlOl/I. andl. 807mg/min respectively. Moreover, KCl, NaCl and SDS inhibited the GAD activity remarkably, whereas Ca^2＋ could activate the GAD, this showed that Ca^2＋ enhanced the affinity between enzyme and the substrate.