Aoki T, Sebolt J, Weber G
Biochem Pharmacol. 1982 Mar 15;31(6):927-32. doi: 10.1016/0006-2952(82)90322-7.
The antitumor drug acivicin, L-(alphaS,5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid, in vivo irreversibly inactivated carbamoyl-phosphate synthetase II(glutamine-dependent)(EC 6.3.5.5), the first and rate-limiting enzyme of de novo pyrimidine nucleotide biosynthesis, in transplantable rat hepatoma and host liver. With two injections of 0.5 mg acivicin per 100 g body weight to one group and two injections of 5 mg to another group, enzyme activity decreased to 20 and 1% in hepatoma and to 99 and 31% in liver respectively. Aspartate carbamoyltransferase (EC 2.1.3.2) activity was not affected. Acivicin in vitro selectively inactivated glutamine-dependent activity of the synthetase II from the hepatoma and liver, with an inactivation constant (Kinact) of 90 microM and a minimum inactivation half-time (T) of 0.7 min. The inactivation velocity with 10 microM acivicin was 5.0-fold stimulated by 2 mM MgATP and 18.4-fold by 2 mM MgATP plus 16.7 mM bicarbonate. MgATP at 0.5 mM caused half-maximum stimulation of the inactivation velocity. Under in vitro conditions, L-glutamine (1 mM) protected the enzyme from inactivation by 10 microM acivicin. The synthetase activity was protected in vitro by 6 mM concentrations for glycine (84%), L-glutamate (59%) and L-aspartate (51%) and by 0.5 mM UTP (35%) from inactivation by 20 microM acivicin. The results are compatible with the suggestion that acivicin is an active site-directed affinity analog of L-glutamine.
抗肿瘤药物阿西维辛，即L-(αS,5S)-α-氨基-3-氯-4,5-二氢-5-异恶唑乙酸，在体内可使移植性大鼠肝癌组织和宿主肝脏中的氨甲酰磷酸合成酶II（谷氨酰胺依赖性）（EC 6.3.5.5）不可逆失活，该酶是从头嘧啶核苷酸生物合成的首个限速酶。给一组大鼠每100克体重注射两次0.5毫克阿西维辛，给另一组大鼠每100克体重注射两次5毫克阿西维辛，结果肝癌组织中的酶活性分别降至20%和1%，肝脏中的酶活性分别降至99%和31%。天冬氨酸氨甲酰转移酶（EC 2.1.3.2）的活性未受影响。阿西维辛在体外可选择性地使肝癌组织和肝脏中的合成酶II的谷氨酰胺依赖性活性失活，失活常数（Kinact）为90微摩尔，最小失活半衰期（T）为0.7分钟。10微摩尔阿西维辛的失活速度在2毫摩尔MgATP存在时被刺激5.0倍，在2毫摩尔MgATP加16.7毫摩尔碳酸氢盐存在时被刺激18.4倍。0.5毫摩尔的MgATP可使失活速度达到最大刺激的一半。在体外条件下，1毫摩尔L-谷氨酰胺可保护该酶不被10微摩尔阿西维辛失活。6毫摩尔浓度的甘氨酸（84%）、L-谷氨酸（59%）和L-天冬氨酸（51%）以及0.5毫摩尔UTP（35%）在体外可保护合成酶活性不被20微摩尔阿西维辛失活。这些结果与阿西维辛是L-谷氨酰胺的活性位点导向亲和类似物这一观点相符。
