Johnson B D, Stankovich M T
Department of Chemistry, Kolthoff and Smith Halls, University of Minnesota, Minneapolis 55455.
Biochemistry. 1993 Oct 12;32(40):10779-85. doi: 10.1021/bi00091a032.
The objective of this work was to identify the key structural functionalities of substrate or product that modulate the thermodynamic properties of medium-chain acyl-CoA dehydrogenase (MCAD). In order to achieve this, two classes of substrate analogues, acetyl-CoA and thioether-CoAs, were complexed with MCAD and their effects on the redox properties of MCAD were measured. A pH dependence study of the redox potential of uncomplexed MCAD allowed us to compare redox properties between complexed and uncomplexed MCAD and to calculate the dissociation constants of the analogues to the three redox states of MCAD. The results from this work indicate that these analogues are not influencing the thermodynamic behavior of MCAD in the same way as natural substrate. Thus, we propose that the following two key structural features of the binding ligand are necessary for mimicking the thermodynamic effects natural substrate has on MCAD: a thioester carbonyl on carbon 1 and a fatty acyl-CoA chain length around 8 carbon units. Furthermore, with the advent of structural knowledge, insights into the interactions of these structural features with MCAD and their influence on MCAD's highly regulated dehydrogenation mechanism are discussed.
这项工作的目的是确定调节中链酰基辅酶A脱氢酶（MCAD）热力学性质的底物或产物的关键结构功能。为了实现这一目标，将两类底物类似物，即乙酰辅酶A和硫醚辅酶A，与MCAD复合，并测量它们对MCAD氧化还原性质的影响。对未复合的MCAD氧化还原电位的pH依赖性研究使我们能够比较复合和未复合的MCAD之间的氧化还原性质，并计算类似物与MCAD三种氧化还原状态的解离常数。这项工作的结果表明，这些类似物对MCAD热力学行为的影响方式与天然底物不同。因此，我们提出，结合配体的以下两个关键结构特征对于模拟天然底物对MCAD的热力学效应是必要的：碳1上的硫酯羰基和大约8个碳单元的脂肪酰基辅酶A链长度。此外，随着结构知识的出现，还讨论了对这些结构特征与MCAD相互作用及其对MCAD高度调控的脱氢机制影响的见解。
