Raushel F M, Anderson P M, Villafranca J J
Biochemistry. 1978 Dec 26;17(26):5587-91. doi: 10.1021/bi00619a001.
The kinetic mechanism of Escherichia coli carbamoyl-phosphate synthetase has been determined at pH 7.5, 25 degrees C. With ammonia as the nitrogen source, the initial velocity and product inhibition patterns are consistent with the ordered addition of MgATP, HCO3-, and NH3. Phosphate is then released and the second MgATP adds to the enzyme, which is followed by the ordered release of MgADP, carbamoyl phosphate, and MgADP. With glutamine as the ammonia donor, the patterns are consistent with a two-site mechanism in which glutamine binds randomly to the small molecular weight subunit producing glutamate and ammonia. Glutamate is released and the ammonia is transferred to the larger subunit. Carbamoyl-phosphate synthetase has also been shown to require a free divalent cation for full activity.
已在pH 7.5、25℃条件下测定了大肠杆菌氨甲酰磷酸合成酶的动力学机制。以氨作为氮源时，初始速度和产物抑制模式与MgATP、HCO₃⁻和NH₃的有序添加一致。然后释放出磷酸，第二个MgATP添加到酶上，随后依次释放出MgADP、氨甲酰磷酸和MgADP。以谷氨酰胺作为氨供体时，模式与双位点机制一致，即谷氨酰胺随机结合到小分子量亚基上产生谷氨酸和氨。谷氨酸被释放，氨转移到大亚基上。氨甲酰磷酸合成酶还被证明需要游离二价阳离子才能具有完全活性。
