【摘要】 根据五株大腸杆菌在不同成分与pH的培养基內培养的結果,选择了pH7.5的牛肉湯加蛋白腖与琼脂的固体培养作为細菌培养条件。从18—20小时在37度培养的大腸杆菌制成了高产量的专一性谷氨酸脫羧酶丙酮粉,其最适pH为5.1,米氏常数为4.3×10^-3M。拟定了一种血清及动物組織中轉氨基酶的測定法。此方法是利用大腸杆菌谷氨酸脫羧酶丙酮粉测定轉氨基作用所生成的谷氨酸量。应用此方法測得我国正常成人血清的谷門轉氨基酶活性为0.70±0.22单位与谷丙轉氨基酶活性为0.58±0.25单位（每单位等于在37度轉氨基作用生成1微克分子L-谷氨酸/1毫升血清/1小时）。应用此方法也試測了大白鼠六种組織中五种氨基酸对α-酮戊二酸的轉氨基酶活性。更多还原

【Abstract】 The effects of the composition and pH of different culture media on the amino acid decarboxylase of five strains of E. coli were studied, and a solid medium consisting of beef broth, peptone（1%） and agar（2%） at pH 7.5 was selected to cultivate the bacteria for preparing L-glutamic acid decarboxylase. An acetone powder was prepared from E. coli grown in the solid medium at 37℃ for 18-20 hours. It decarboxylated L-glutamic acid with a high specificity.It was found that the solid medium was preferable to liquid ones in the cultivation of E. coli for the production of specific L-glutamic acid decarboxylase. E. coli grown in the liquid medium of beef-peptone or casein digest always produced decarboxylases of glutamic acid, glutamine, arginine and lysine. But in the solid medium, it produced only the decarboxylases of L-glutamate and L-glutamine and no induced decarboxylase of either arginine or lysine was formed. Besides, the activity of the glutamine decarboxylase vanished upon subsequently converting the preparation into dry acetone powder. The glutamic acid decarboxylase in the E. coli acetone powder so prepared was found to have an optimal pH of 5.1 and a Michaelis constant of 4.3×10^-3M.A method involving the use of the glutamic decarboxylase in the form of E. coli acetone powder is introduced for the determination of glutamate transaminase in blood and tissues: Samples of blood sera or tissue homogenates are incubated with an excess of amino-acid and α-ketoglutarate at 37℃ for a definite period of time, the L-glutamic acid produced is decarboxylated by the acetone powder and the volume of CO₂ liberated is measured in the Warburg apparatus. The activity of the transaminase is then calculated in terms of micromoles of L-glutamic acid produced per unit amount of the analyzed sample（1ml. of blood or 1g. of tissue） per hour of incubation at 37℃.The glutamate-oxaloacetate and glutamate-pyruvate transaminases of the blood sera of twenty normal human subjects were determined by the above method giving average values of 0.7±0.22 and 0.5±0.25 units respectively. The application of this method was also demonstrated in the determination of the transaminase activity on five amino acids with α-ketoglutarate in six different tissues of rat.更多还原