SUPEROXIDE ION AS A PRIMARY REDUCTANT IN ASCORBATE-MEDIATED FERRITIN IRON RELEASE
SUPEROXIDE ION AS A PRIMARY REDUCTANT IN ASCORBATE-MEDIATED FERRITIN IRON RELEASE
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DOI：
10.1016/0891-5849(87)90017-7
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发表时间：
1987-01-01
影响因子：
7.4
通讯作者：
MCCLEARY, CJ
中科院分区：
文献类型：
--
作者：
BOYER, RF;MCCLEARY, CJ
研究了有氧条件下抗坏血酸促进铁蛋白铁还原的机理。通过分光光度法测量在562 nm处吸收的Fe（ferrozine）32+络合物来确定铁蛋白铁释放的初始速率。初始亚铁嗪浓度的变化没有影响铁的释放速率，这表明亚铁嗪不参与速率决定步骤。铁释放的初始速率作为抗坏血酸盐浓度的函数的实验测量结果导致饱和动力学，Vmax = 2.0 × 10 - 4。10-7 M. cntdot. min-1，Km = 1.3 × 1.5。10-3 M. pH值的影响是相当明显的，在pH 7.0的铁释放的最大速率。化学计量测量的反应混合物，与添加的过氧化氢酶，导致在2 Fe（II）释放每抗坏血酸的比率。抗坏血酸介导的铁释放被超氧化物歧化酶抑制85%，但0%的抑制与aposuperoxide歧化酶。有人提出，超氧离子，铁促进抗坏血酸氧化过程中产生的，作为铁蛋白铁的还原剂。与这些实验观察一致的铁蛋白铁释放的机制进行了讨论。
The mechanism of ascorbate-promoted ferritin iron reduction under aerobic conditions was studied. The initial rate of ferritin iron release was determined by spectrophotometric measurement of the Fe(ferrozine)32+ complex which absorbs at 562 nm. Variation of the initial ferrozine concentration had no influence on the rate of iron release suggesting that ferrozine does not participate in the rate-determining step. Experimental measurements of the initial rate of iron release as a function of ascorbate concentration resulted in saturation kinetics with Vmax = 2.0 .times. 10-7 M .cntdot. min-1 and Km = 1.3 .times. 10-3 M. The effect of pH was quite pronounced with a maximal rate of iron release at pH 7.0. Stoichiometric measurements on the reaction mixture, with added catalase, resulted in a ratio of 2 Fe(II) released per ascorbate. Ascorbate-mediated iron release was inhibited 85% by superoxide dismutase, but 0% inhibition was noted with aposuperoxide dismutase. It is proposed that superoxide ion, generated during the iron-promoted oxidation of ascorbate, acts as a reductant of ferritin iron. A mechanism of ferritin iron release consistent with these experimental observations is discussed.