Szweda L I, Stadtman E R
Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892.
Arch Biochem Biophys. 1993 Mar;301(2):391-5. doi: 10.1006/abbi.1993.1161.
Incubation of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides with Fe2+ and citrate results in rapid O2-dependent inactivation of the enzyme. Maximal rate of inactivation occurred at equimolar concentrations of Fe2+ and citrate. Loss of enzyme activity appears to be the result of selective oxidative modification, as evidenced by a corresponding increase in protein carbonyl content. Partially inactivated enzyme remained predominantly in the dimeric form with no change in the apparent affinity of the remaining active subunits for substrate. Modified Glu-6-PDH was, however, more susceptible to heat denaturation. Our results suggest that the Fe(2+)-citrate complex binds to the glucose 6-phosphate binding site and then undergoes reaction with H2O2 formed in solution leading to the oxidative modification of amino acids essential for enzyme activity.
将来自肠系膜明串珠菌的葡萄糖-6-磷酸脱氢酶与Fe2+和柠檬酸盐一起温育，会导致该酶迅速发生依赖于O2的失活。在Fe2+和柠檬酸盐等摩尔浓度下，失活速率达到最大值。酶活性的丧失似乎是选择性氧化修饰的结果，蛋白质羰基含量相应增加证明了这一点。部分失活的酶主要仍以二聚体形式存在，剩余活性亚基对底物的表观亲和力没有变化。然而，修饰后的Glu-6-PDH对热变性更敏感。我们的结果表明，Fe(2+)-柠檬酸盐复合物与葡萄糖6-磷酸结合位点结合，然后与溶液中形成的H2O2发生反应，导致对酶活性至关重要的氨基酸发生氧化修饰。
