Kinetic ferroxidase

Theil, E.C. and Huynh, B.H. (1998) Direct spectroscopic and kinetic evidence for the involvement of a peroxodiferric intermediate during the ferroxidase reaction in fast ferritin mineralization. Biochemistry, 37, 9871-9876. 

Iron is oxidized for incorporation into the mineralized core by either a protein enzymatic mechanism involving a putative dinuclear Fe ferroxidase site on the H chain subunit or a mineral surface mechanism. The net stoichiometric reactions for the two kinetic pathways are given by the following equations ... 

Fig. 4. Analysis of the kinetic constants of the ferroxidase reaction catalyzed by soluble Fet3p. Fe(II) oxidation (A) and O2 consumption (B) were measured continuously and the residual substrate concentration was plotted with respect to time according to the integrated form of the Michealis-Menten equation as indicated in each panel. Fe(II) oxidation was followed by the appearance of Fe(III) at 315 nm while O2 consumption was determinedby the use of an O2 electrode. The [Fet3p] =0.2 fcM in 0.1 M MES buffer, pH 6.0, at 25°C. The curve in each panel is a linear least-squares fit of the data to...

Cartwright and Wintrobe and their co-workers suggested a link between copper deficiency and anemia in mammals 50 years ago (see Lahey et al., 1952). Cartwright subsequently demonstrated that this copper-dependent anemia was unresponsive to iron supplementation but was corrected on administration of ceruloplasmin (see Lee et al., 1968). The molecular basis of this link was indicated by Osaki and Friedan, who characterized the ferroxidase activity of ceruloplasmin and kinetically demonstrated that Cp could play a critical role in catalyzing trafficking of the potentially cytotoxic Fe(II) in the plasma to apoA f (see Frieden and... 

Osaki, 1974 Osaki, 1966 Osaki et al., 1966). Using the kinetic values given above, they estimated that without the ferroxidase activity of Cp in the plasma 80% of the iron released from erythrocyte turnover would accumulate as non-Tf-bound Fe(ll) and thereby would be unavailable for reabsorption by the reticuloendothelial system. Furthermore, this free Fe(II) could catalyze the formation of reactive oxygen species via the Fenton reaction. This, in turn, could lead to a subsequent organismal pathophysiology (Miyajima et al., 1996 Nakano, 1993). This inference has been strikingly confirmed by research over the past 6 years in both yeasts and mammals this research has directly tested the hypothesis that multicopper oxidase-dependent ferroxidase activity is essential to eukaryotic iron homeostasis (Askwith et al., 1996 Harris et al., 1995 1998 Wessling-Resnick, 1999). 

Kinetic Constants for the Fet3p Ferroxidase Reaction in Vitro and Fe Uptake in Vivo... 

Hassett, R. E, Yuan, D. S., and Kosman, D. J. (1998). Spectral and kinetic properties of the Fet3 protein from Saccharomyces cerevisiae, a multinuclear copper ferroxidase enzyme. J. Biol. Chem. 273, 23274-23282. 

Osaki, S. (1966). Kinetic studies of ferrous ion oxidation with crystalline human ferroxidase (ceruloplasmin)./. Biol. Chem. 241, 5053-5059. 

Table VII. Kinetic Characteristics of the Inhibition of Ferroxidase by the Strongest Metal Ion Inhibitors ...

Kinetic experiments with recombinant HuHF as well as with HuLF and HoLF have further substantiated the proposal that the dinuclear center is the ferroxidase center (see Figure... 

Huber CT, Frieden E. Substrate activation and the kinetics of ferroxidase. J Biol Chem 1970 245 3973-3978. 

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