Attwood P V, Graneri B D
Department of Biochemistry, University of Western Australia, Nedlands.
Biochem J. 1991 Jan 15;273(Pt 2)(Pt 2):443-8. doi: 10.1042/bj2730443.
In a reaction that is analogous to the phosphorylation of ADP from carboxyphosphate, pyruvate carboxylase catalyses the formation of ATP from carbamoyl phosphate and ADP at a rate that is about 0.3% of the pyruvate-carboxylation reaction and about 3% of the full reverse reaction. Acetyl-CoA stimulates the phosphorylation of ADP from carbamoyl phosphate but is not an essential requirement of the reaction. Mg2+ also stimulates the reaction, and in the range of Mg2+ concentrations considered the effect of V is much larger in the absence of acetyl-CoA than in its presence. Acetyl-CoA and Mg2+ may be acting in a co-operative way to stimulate the phosphorylation of ADP in a similar way to their effects on the pyruvate-carboxylation reaction. The phosphorylation of ADP by carbamoyl phosphate is also stimulated by the presence of biotin in the part of the active site where this reaction occurs, but again it is not absolutely required for the reaction to proceed. The pH profiles of the phosphorylation of ADP by carbamoyl phosphate indicate that there are at least two ionizable residues involved in the reaction, one of which probably has a role in the release of carbamate from the active site.
在一个类似于由羧基磷酸将ADP磷酸化的反应中，丙酮酸羧化酶催化由氨甲酰磷酸和ADP形成ATP，其反应速率约为丙酮酸羧化反应的0.3%，约为完全逆反应的3%。乙酰辅酶A刺激由氨甲酰磷酸将ADP磷酸化，但不是该反应的必需条件。Mg2+也刺激该反应，在所考虑的Mg2+浓度范围内，在没有乙酰辅酶A的情况下V的影响比有乙酰辅酶A时大得多。乙酰辅酶A和Mg2+可能以协同方式起作用，以类似于它们对丙酮酸羧化反应的影响来刺激ADP的磷酸化。在发生该反应的活性位点部分，生物素的存在也刺激氨甲酰磷酸将ADP磷酸化，但同样，该反应的进行并非绝对需要生物素。氨甲酰磷酸将ADP磷酸化的pH曲线表明，该反应至少涉及两个可电离的残基，其中一个可能在从活性位点释放氨基甲酸酯方面起作用。
