Burgner J W, Ray W J
Biochemistry. 1978 May 2;17(9):1654-61. doi: 10.1021/bi00602a012.
The binary complex of NAD+ and dogfish A4 lactate dehydrogenase reacts reversibly with pyruvate enol to produce an inactive, enzyme-adduct complex, in which the nicotinamide and pyruvate moieties are linked by means of a covalent bond. This process is examined in both the forward and reverse directions as a function of reactant and buffer concentrations at pH 7, under conditions where the enolization of pyruvate is at equilibrium, and the involvement of complexes with stoichiometry E.NAD, E.NAD.PyrE, and E.NAD.PyrK is defined. (The subscripts, E and K, indicate the enol and keto forms of pyruvate.) One pathway for formation of the adduct complex involves the prior formation of the E.NAD.PyrE complex from E.NAD and pyruvate enol; the alternative pathway involves formation of the same complex via the enolization of E.NAD.PyrK, a process that is catalyzed by an external (nonenzymic) base. The possible use of the adduct reaction as a model for the normal enzymic reaction is considered.
NAD⁺与角鲨A4乳酸脱氢酶的二元复合物与丙酮酸烯醇可逆反应，生成一种无活性的酶加合物复合物，其中烟酰胺和丙酮酸部分通过共价键相连。在pH 7的条件下，当丙酮酸的烯醇化处于平衡时，根据反应物和缓冲液浓度，对该过程的正向和反向进行研究，并确定化学计量比为E.NAD、E.NAD.PyrE和E.NAD.PyrK的复合物的参与情况。（下标E和K分别表示丙酮酸的烯醇式和酮式。）加合物复合物形成的一条途径涉及由E.NAD和丙酮酸烯醇预先形成E.NAD.PyrE复合物；另一条途径涉及通过E.NAD.PyrK的烯醇化形成相同的复合物，该过程由外部（非酶）碱催化。考虑了将加合物反应用作正常酶促反应模型的可能性。
