Leisinger T, Haas D
J Biol Chem. 1975 Mar 10;250(5):1690-3.
N-Acetylglutamate synthase, the first enzyme of arginine biosynthesis, was stabilized in crude extracts from Escherichia coli. At 4 degrees the enzyme lost less than 5% of activity per day. L-Arginine repressed the formation of N-acetylglutamate synthase. Under conditions of genetic or physiological derepression, a specific activity of approximately 50 nmol per min per mg of protein was measured. No activity (i.e. less than 0.2 nmol per min per mg of protein) could be detected in extracts from cells grown under conditions of repression, whereas an intermediate level was found in cell cultivated on minimal medium. In a 6-fold purified preparation L-arginine inhibited the enzyme. Of 11 precursors and analogues of arginine tested only O-[L-norvalyl-5]-isourea inhibited N-acetylglutamate synthase as strongly as L-agrinine.
N-乙酰谷氨酸合酶是精氨酸生物合成的首个酶，在大肠杆菌的粗提取物中得到了稳定。在4℃时，该酶每天活性损失不到5%。L-精氨酸抑制N-乙酰谷氨酸合酶的形成。在基因或生理去阻遏条件下，测得的比活性约为每分钟每毫克蛋白质50纳摩尔。在阻遏条件下生长的细胞提取物中未检测到活性（即每分钟每毫克蛋白质低于0.2纳摩尔），而在基本培养基上培养的细胞中发现了中间水平。在6倍纯化的制剂中，L-精氨酸抑制该酶。在测试的11种精氨酸前体和类似物中，只有O-[L-正缬氨酰-5]-异脲对N-乙酰谷氨酸合酶的抑制作用与L-精氨酸一样强。
