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.