Possible occurrence and role of an essential histidyl residue in succinate dehydrogenase.
Possible occurrence and role of an essential histidyl residue in succinate dehydrogenase.
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DOI：
10.1073/pnas.78.11.6749
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发表时间：
1981-11
影响因子：
11.1
通讯作者：
S. Vik;Y. Hatefi
中科院分区：
文献类型：
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作者：
S. Vik;Y. Hatefi
二乙基戊二酸（ET2PC）抑制琥珀酸脱氢酶[琥珀酸酯：（受体）氧化还原酶，EC 1.3.99.1] combistochochondrial颗粒的活性，复合物II（琥珀酸酯：泛素氧化氧化还原酶），以及溶解性辅助硅质，纯sixucation，纯sixute，纯，纯脱脂酶。相对于ET2PC浓度的反应顺序接近统一，表明每个酶的活性单位的一个基本残基修改。 ET2PC抑制作用的pH谱，羟胺抑制的部分逆转以及紫外线区域中ET2PC处理的酶的光谱变化表明修饰了组酰基残基。琥珀酸脱氢酶活性可以通过琥珀酸，富马酸盐，丙酸酯或草乙酸盐抑制ET2PC抑制（也通过激活诸如ClO4（ - ）和BR-）等阴离子的抑制，这表明ET2PC修饰的基本残基可能在活性部位。在combisochochondrial颗粒和纯化的酶中，琥珀酸脱氢酶活性在pH大于或等于7.0时最高且相对恒定，并且在pH下急剧下降小于7.0。相比之下，富马酸盐还原酶活性在pH值小于或等于7.0时最高，并且pH值大于7.0。这些结果与推定的组酰基残基的咪唑部分的未塑料和质子化形式的可能参与是一致的，该形式分别参与了琥珀酸氧化和富马酸酸盐还原。
Diethylpyrocarbonate (Et2PC) inhibits the succinate dehydrogenase [succinate:(acceptor) oxidoreductase, EC 1.3.99.1] activity of submitochondrial particles, Complex II (succinate:ubiquinone oxidoreductase), and the soluble, pure succinate dehydrogenase. The reaction order with respect to Et2PC concentration is close to unity, suggesting modification of one essential residue per active unit of the enzyme. The pH profile of Et2PC inhibition, the partial reversal of inhibition by hydroxylamine, and the spectral change of the Et2PC-treated enzyme in the UV region suggest modification of a histidyl residue. Succinate dehydrogenase activity can be protected against Et2PC inhibition by succinate, fumarate, malonate, or oxaloacetate (also by activating anions such as ClO4(-) and Br-), suggesting that the Et2PC-modified essential residue might be at the active site. In both submitochondrial particles and the purified enzyme, succinate dehydrogenase activity is highest and relatively constant at pH greater than or equal to 7.0 and diminishes precipitously at pH less than 7.0. By contrast, fumarate reductase activity is highest at pH less than or equal to 7.0 and diminishes at pH greater than 7.0. These results are consistent with the possible participation of the unprotonated and protonated forms of the imidazole moiety of the putative histidyl residue, respectively, in succinate oxidation and fumarate reduction.