Raushel F M, Anderson P M, Villafranca J J
J Biol Chem. 1978 Oct 10;253(19):6627-9.
Carbamyl phosphate synthetase from Escherichia coli has been shown to use only the A isomer of adenosine-5'-[2-thiotriphosphate] in both the ATPase reaction (MgATP HCO3- leads to MgADP + Pi) and the carbamyl phosphate synthesis reaction (2MgATP + HCO3- + L-glutamine leads to 2MgADP + Pi + carbamyl-P + L-glutamate). The B isomer was less than 5% as reactive. In the reverse reaction, only the A isomer of adenosine-5'-[2-thiotriphosphate] is synthesized from adenosine-5'-[2-thiodiphosphate] and carbamyl-P as determined by 31P NMR and a coupled enzymatic assay with Cd2+- hexokinase. It is therefore proposed that carbamyl phosphate synthetase uses the same diastereomer of MgATP at both ATP sites.
已证明来自大肠杆菌的氨甲酰磷酸合成酶在ATP酶反应（MgATP + HCO₃⁻ → MgADP + Pi）和氨甲酰磷酸合成反应（2MgATP + HCO₃⁻ + L - 谷氨酰胺 → 2MgADP + Pi + 氨甲酰 - P + L - 谷氨酸）中仅使用腺苷 - 5'-[2 - 硫代三磷酸]的A异构体。B异构体的反应活性不到5%。在逆反应中，通过³¹P NMR以及与Cd²⁺ - 己糖激酶的偶联酶促测定确定，仅从腺苷 - 5'-[2 - 硫代二磷酸]和氨甲酰 - P合成腺苷 - 5'-[2 - 硫代三磷酸]的A异构体。因此，有人提出氨甲酰磷酸合成酶在两个ATP位点使用相同的MgATP非对映异构体。
