Minton A P, Wilf J
Biochemistry. 1981 Aug 18;20(17):4821-6. doi: 10.1021/bi00520a003.
The specific activity of rabbit muscle glyceraldehyde-3-phosphate dehydrogenase (GAPD) has been measured as a function of GAPD concentration in the absence and presence of 18 g/dL ribonuclease A. The specific activity of GAPD at fixed concentration has been measured as a function of the concentration of added ribonuclease A, beta-lactoglobulin, bovine serum albumin, and poly(ethylene glycol) (Mr 20000) at additive concentrations of up to 30 g/dL. All of the data may be semiquantitatively accounted for by a simple model based upon the following qualitative assumptions: (1) Under the conditions of the reported experiments, GAPD exists primarily as an equilibrium mixture of monomers and tetramers of GAPD subunits. (2) The monomers have a much larger specific activity than do the tetramers. (3) The addition of high concentrations of unrelated globular proteins does not affect the activity of either monomer or tetramer but does promote the formation of tetramer due to space-filling properties of the added species, as proposed by Minton [Minton, A. P. (1981) Biopolymers (in press)].
在不存在和存在18 g/dL核糖核酸酶A的情况下，已测定了兔肌肉甘油醛-3-磷酸脱氢酶（GAPD）的比活性与GAPD浓度的函数关系。在添加浓度高达30 g/dL的情况下，已测定了固定浓度下GAPD的比活性与添加的核糖核酸酶A、β-乳球蛋白、牛血清白蛋白和聚乙二醇（Mr 20000）浓度的函数关系。所有数据都可以通过一个基于以下定性假设的简单模型进行半定量解释：（1）在所报道的实验条件下，GAPD主要以GAPD亚基的单体和四聚体的平衡混合物形式存在。（2）单体的比活性比四聚体大得多。（3）如Minton所提出的[Minton, A. P. (1981) Biopolymers (即将发表)]，添加高浓度的无关球状蛋白不会影响单体或四聚体的活性，但由于添加物种的空间填充特性，确实会促进四聚体的形成。
