The effect of ionic environment on pig heart mitochondrial malate dehydrogenase was investigated by means of two low resolution conformational probes, thermal stability and proteolytic liability. 2. High ionic strength and high enzyme concentrations stabilize the enzyme towards thermal inactivation, probably by maintaining the enzyme in the dimeric form. 3. Proteolysis of malate dehydrogenase under conditions where the enzyme is thermally stable indicates a secondary ionic effect on structure. 4. Attempts to demonstrate dissociation of native malate dehydrogenase dimer into its constituent subunits using gel filtration on Sephacryl S-200 proved inconclusive. At low ionic strength malate dehydrogenase does not exhibit normal gel filtration behaviour.
摘要
通过热稳定性和蛋白水解敏感性这两种低分辨率构象探针，研究了离子环境对猪心脏线粒体苹果酸脱氢酶的影响。2. 高离子强度和高酶浓度可使酶对热失活具有稳定性，这可能是通过将酶维持在二聚体形式实现的。3. 在酶热稳定的条件下对苹果酸脱氢酶进行蛋白水解，表明对结构存在二级离子效应。4. 尝试使用Sephacryl S - 200凝胶过滤法证明天然苹果酸脱氢酶二聚体解离成其组成亚基，但结果尚无定论。在低离子强度下，苹果酸脱氢酶不表现出正常的凝胶过滤行为。
