Hsieh Ju-Yi, Liu Jyung-Hurng, Yang Pai-Chun, Lin Chi-Li, Liu Guang-Yaw, Hung Hui-Chih
Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan.
Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan; Institute of Genomics and Bioinformatics, National Chung Hsing University, Taichung, Taiwan.
PLoS One. 2014 Jun 9;9(6):e98385. doi: 10.1371/journal.pone.0098385. eCollection 2014.
Human mitochondrial NAD(P)+-dependent malic enzyme (m-NAD(P)-ME) is allosterically activated by the four-carbon trans dicarboxylic acid, fumarate. Previous studies have suggested that the dicarboxylic acid in a trans conformation around the carbon-carbon double bond is required for the allosteric activation of the enzyme. In this paper, the allosteric effects of fumarate analogs on m-NAD(P)-ME are investigated. Two fumarate-insensitive mutants, m-NAD(P)-ME_R67A/R91A and m-NAD(P)-ME_K57S/E59N/K73E/D102S, as well as c-NADP-ME, were used as the negative controls. Among these analogs, mesaconate, trans-aconitate, monomethyl fumarate and monoethyl fumarate were allosteric activators of the enzyme, while oxaloacetate, diethyl oxalacetate, and dimethyl fumarate were found to be allosteric inhibitors of human m-NAD(P)-ME. The IC50 value for diethyl oxalacetate was approximately 2.5 mM. This paper suggests that the allosteric inhibitors may impede the conformational change from open form to closed form and therefore inhibit m-NAD(P)-ME enzyme activity.
人线粒体烟酰胺腺嘌呤二核苷酸（磷酸）依赖的苹果酸酶（m-NAD(P)-ME）受四碳反式二羧酸富马酸酯变构激活。先前的研究表明，碳-碳双键周围呈反式构象的二羧酸是该酶变构激活所必需的。本文研究了富马酸酯类似物对m-NAD(P)-ME的变构效应。两个对富马酸酯不敏感的突变体m-NAD(P)-ME_R67A/R91A和m-NAD(P)-ME_K57S/E59N/K73E/D102S，以及胞质NADP-苹果酸酶（c-NADP-ME）用作阴性对照。在这些类似物中，中康酸、反乌头酸、单甲基富马酸酯和单乙基富马酸酯是该酶的变构激活剂，而草酰乙酸、二乙基草酰乙酸和富马酸二甲酯被发现是人m-NAD(P)-ME的变构抑制剂。二乙基草酰乙酸的IC50值约为2.5 mM。本文表明，变构抑制剂可能会阻碍从开放形式到封闭形式的构象变化，从而抑制m-NAD(P)-ME酶的活性。
