SUPEROXIDE ION AS A PRIMARY REDUCTANT IN ASCORBATE-MEDIATED FERRITIN IRON RELEASE

被引：137

作者：

BOYER, RF

MCCLEARY, CJ

机构：

[1] Department of Chemistry, Hope College, Holland

来源：

FREE RADICAL BIOLOGY AND MEDICINE | 1987年 / 3卷 / 06期

关键词：

Ferritin Ascorbate; Hydroxyl radical; Iron; Reduction; Superoxide ion;

D O I：

10.1016/0891-5849(87)90017-7

中图分类号：

Q5 [生物化学]; Q7 [分子生物学];

学科分类号：

071010 ; 081704 ;

摘要：

The mechanism of ascorbate-promoted ferritin iron reduction under aerobic conditions was studied. The unitial 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 × 10-7 M · min-1 and KM = 1.3 × 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. © 1987.

引用

页码：389 / 395

页数：7

共 40 条

[1]

Theil, Ferritin: structure, function, and regulation, Iron binding proteins without cofactors or sulfur clusters, pp. 1-38, (1983)

[2]

Harrison, The structure and function of ferritin, Biochem. Ed., 14, pp. 154-162, (1986)

[3]

Ford, Harrison, Rice, Smith, Treffry, White, Yariv, Ferritin: design and formation of an iron-storage molecule, Philis. Trans. Soc. Lond., 304, pp. 551-565, (1984)

[4]

Harrison, Treffry, Lilley, Ferritin as an iron-storage protein: mechanicms of iron uptake, J. Inorg. Biochem., 27, pp. 287-293, (1986)

[5]

Niederer, Ferritin: iron incorporation and iron release, Experientia, 26, pp. 218-220, (1970)

[6]

Wardeska, Viglione, Chasteen, Metal ion complexes of apoferritin, J. Biol. Chem., 261, pp. 6677-6683, (1986)

[7]

Crichton, Roman, Roland, Paques, Paques, Vandamme, Ferritin iron deposition and mobilization, J. Mol. Cat., 7, pp. 267-276, (1980)

[8]

Chasteen, Antanaitis, Aisten, Iron deposition in apoferritin, J. Biol. Chem., 260, pp. 2926-2929, (1985)

[9]

Boyer, Schori, The incorporation of iron into apoferritin as mediated by ceruloplasmin, Biochem. Biophys. Res. Commun., 116, pp. 244-250, (1983)

[10]

Bakker, Boyer, Iron incorporation into apoferritin. The role of apoferritin as a ferroxidase, J. Biol. Chem., 261, pp. 13182-13185, (1986)

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