Jensen W A, Armstrong J M, De Giorgio J, Hearn M T
Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
Biochim Biophys Acta. 1996 Aug 15;1296(1):23-34. doi: 10.1016/0167-4838(96)00049-0.
The effect of different salts and amino acids on the thermal stability and quaternary conformation of pig heart mitochondrial malate dehydrogenase (phm-MDH) in solution has been determined. The effectiveness of salts of anions in the stabilisation of phm-MDH followed the order: Citrate > SO(4)2- > or = Tartrate > Phosphate > F-, CH3COO- > Cl- > Br-. Anions above and including Cl- in this series were increasingly effective in stabilising phm-MDH with a rise in salt concentration from 0.05-2 M, whilst Br- was destabilising under similar conditions. The effect of potassium salts of acetate, chloride and bromide at a concentration of 1 M on the quaternary conformation of phm-MDH correlated also with the relative order of anion stabilisation above, with the anions higher in the series increasingly promoting the formation of the dimeric conformation of the enzyme. The cations of the corresponding salts had a relatively neutral (Cs+, K+, Na+, (CH3)4N+, NH4+) to a destabilising ((CH3)4N+, NH4+, Li+) effect on phm-MDH. Potassium ferrocyanide and potassium ferricyanide conferred complex, concentration dependent effects on the stability of phm-MDH, unlike the salts described above. Salts of amino acids were effective in the stabilisation of phm-MDH against temperature induced changes, following the order: NaGlutamatec = NaAspartate > NaGlycinate > lysine. HCl > arginine. HCl. The magnitudes and trends of the effects of these salts and amino acids on the stability and quaternary structure of phm-MDH were observed to correlate well with considerations based on the Hofmeister series of anions and solvophobic concepts as they apply to the influence of co-solvents at intermediate to higher concentrations. Other, more specific effects were also evident in the stabilisation and destabilisation of phm-MDH by low concentrations of the salts, as noted most particularly in the presence of potassium ferrocyanide and potassium ferricyanide.
已测定不同盐类和氨基酸对溶液中猪心线粒体苹果酸脱氢酶（phm-MDH）热稳定性和四级构象的影响。阴离子盐对phm-MDH的稳定作用顺序为：柠檬酸盐＞硫酸根离子≥酒石酸盐＞磷酸盐＞氟离子、醋酸根离子＞氯离子＞溴离子。该系列中氯离子及以上的阴离子，随着盐浓度从0.05 M升至2 M，对phm-MDH的稳定作用逐渐增强，而在类似条件下溴离子则起 destabilising作用。浓度为1 M的醋酸钾、氯化钾和溴化钾对phm-MDH四级构象的影响也与上述阴离子稳定作用的相对顺序相关，该系列中位置较高的阴离子越来越多地促进酶二聚体构象的形成。相应盐类的阳离子对phm-MDH有相对中性（铯离子、钾离子、钠离子、四甲基铵离子、铵离子）到destabilising（四甲基铵离子、铵离子、锂离子）的作用。亚铁氰化钾和铁氰化钾对phm-MDH的稳定性产生复杂的、浓度依赖性的影响，这与上述盐类不同。氨基酸盐对phm-MDH具有抗温度诱导变化的稳定作用，顺序为：谷氨酸钠 = 天冬氨酸钠＞甘氨酸钠＞赖氨酸·盐酸盐＞精氨酸·盐酸盐。观察到这些盐类和氨基酸对phm-MDH稳定性和四级结构的影响程度及趋势，与基于霍夫迈斯特阴离子系列和疏溶剂概念的考量密切相关，因为它们适用于中高浓度共溶剂的影响。低浓度盐类对phm-MDH的稳定和destabilising作用中也明显存在其他更特殊的影响，最显著的是在亚铁氰化钾和铁氰化钾存在的情况下。
