Kinetics of the hemerythrin-oxygen interaction.

Waal, D J De; Wilkins, Ralph G.

doi:10.1016/s0021-9258(17)33592-5

Cited by 44 publications

(20 citation statements)

References 14 publications

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“…It does appear, however, from the limited number of systems so far reported that 02 bonding, as well as being an integral feature of the respiratory process, may act to protect the protein against oxidation. It is also apparent that the deoxy form obtained rapidly (deWaal & Wilkins, 1976) by oxygen dissociation from oxyhemerythrin behaves the same toward Fe(CN)63™ as deoxy obtained by lengthy reduction of methemerythrin.…”

Section: Discussionmentioning

confidence: 82%

“…The dependence of the first-order rate constant k, associated with this stage, on the concentrations of Fe(CN)63" (0.5-12.0 mM) and free 02 (0.20-1.0 mM) is given by (see Figure 4 where A, and k4 are second-order rate constants for reaction of ferricyanide with deoxy-and oxyhemerythrin, respectively. The equilibrium between the deoxy and oxy forms is rapidly attained (deWaal & Wilkins, 1976). Since K{02] > 1, the observed eq 4 is obtained where a = k4 and b = kfK.…”

Section: Gouldii)mentioning

confidence: 99%

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Role of mixed oxidation states in the oxidation of hemerythrin species by ferricyanide ion

Bradić¹,

Harrington²,

Wilkins³

et al. 1980

Biochemistry

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The oxidation of deoxy- and oxyhemerythrin to methemerythrin by Fe(CN)6(3-) has been examined. The first step produces (semi-met)O, a half-oxidized form of hemerythrin which has different spectral and kinetic properties from (semi-met)R which is produced by one-electron reduction of methemerythrin. Further oxidation of (semi-met)O to methemerythrin usually occurs only indirectly via disproportionation of (semi-met)O to met and deoxy forms within the octameric framework. Oxidation of (semi-met)R by Fe(CN)6(3-) is a direct second-order reaction. (Semi-met)O is reduced rapidly by dithionite to deoxy, whereas that of (semi-met)R is a slow biphasic process. The oxidation of oxyhemerythrin occurs via the deoxy species, little, if any, reactivity being attributable to the oxy form. The oxidation of the azide adduct of (semi-met)R is biphasic, in which in step one N3(-) is removed during the oxidation to methemerythrin, which in the second step recombines with N3(-). Rate parameters for all these processes at pH 8.2 and 6.3 for protein from Phascolopsis gouldii and Themiste zostericola have been obtained. The implications of these findings to hemerythrin chemistry are discussed.

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Section: Discussionmentioning

confidence: 82%

Section: Gouldii)mentioning

confidence: 99%

Role of mixed oxidation states in the oxidation of hemerythrin species by ferricyanide ion

Bradić¹,

Harrington²,

Wilkins³

et al. 1980

Biochemistry

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“…For 1a , the value of P 1/2 for dioxygen binding is known (6 Torr at −35 °C) 28 and corresponds to a Δ G value of −9.6 kJ mol -1 . Although the temperature dependence of the binding has not been reported, a crude approximation of 80 J mol -1 K -1 can be made based on the measured values reported for Hr …”

Section: Discussionmentioning

confidence: 99%

Mechanistic Studies of the Formation and Decay of Diiron(III) Peroxo Complexes in the Reaction of Diiron(II) Precursors with Dioxygen

et al. 1996

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Mechanistic studies of the reactions of three analogous alkoxo-bridged diiron(II) complexes with O(2) have been carried out. The compounds, which differ primarily in the steric accessibility of dioxygen to the diiron(II) center, form metastable &mgr;-peroxo intermediates when studied at low temperature. At ambient temperatures, these intermediates decay to form (&mgr;-oxo)polyiron(III) products. The effect of ligand steric constraints on the O(2) reactivity was investigated. When access to the diiron center was unimpeded, the reaction was first-order with respect to both [Fe(II)(2)] and [O(2)] and the activation parameters for O(2) addition were similar to those for O(2) reacting with the dioxygen transport protein hemerythrin. When the binding site was occluded, however, reduced order with respect to [O(2)] was observed and a two-step mechanism was required to explain the kinetic results. Decay of all three peroxide intermediates involves a bimolecular event, implying the formation of tetranuclear species in the transition state.

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“…Thus, unfortunately, the determination of whether or not one iron is pentacoordinate is not discernible within our present experimental limitations. A pentacoordinate iron with a free site for exogenous ligand binding has been implied from spectroscopic and kinetic analysis of deoxyhemerythrin (Reem & Solomon, 1987;de Waal & Wilkins, 1976). Second Shell.…”

Section: R(k)mentioning

confidence: 99%

The active site of hemerythrin as determined by x-ray absorption fine structure

Zhang

Stern²,

Ellis³

et al. 1988

Biochemistry

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Extensive X-ray absorption fine structure measurements and analysis have been made on azidomet- and methemerythrin and on the native forms of oxy- and deoxyhemerythrin. Due to the availability of models that have been synthesized to mimic the active site of hemerythrin, it was possible to make a thorough assessment of the various errors in the structural parameters determined by the analysis. It is found that the largest source of error is the lack of complete transferability of amplitude and phase between the standards and hemerythrin. This is of particular importance in distinguishing the contributions of the second-shell low-Z atoms and, thus, has a substantial influence on the determination of the iron-iron distance. The internal consistencies of the various checks and a new formulation of error analysis for the structural parameters give us confidence in the structure determined for the active site. The main result is that as O2 is released from oxyhemerythrin, the mu-oxo bridge between the two iron atoms in the active site with an Fe-O distance of 1.8 A converts to a mu-hydroxo bridge in deoxyhemerythrin, expanding the Fe-O distance to 2.0 A. The Fe-Fe distance expands proportionally from 3.24 A in oxyhemerythrin to 3.57 A in deoxyhemerythrin so as to keep the Fe-O-Fe bridging angle approximately constant. These conclusions provide experimental support for the structures of oxy- and deoxyhemerythrin proposed previously on the basis of spectroscopic and preliminary X-ray crystallographic data.

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Kinetics of the hemerythrin-oxygen interaction.

Cited by 44 publications

References 14 publications

Role of mixed oxidation states in the oxidation of hemerythrin species by ferricyanide ion

Role of mixed oxidation states in the oxidation of hemerythrin species by ferricyanide ion

Mechanistic Studies of the Formation and Decay of Diiron(III) Peroxo Complexes in the Reaction of Diiron(II) Precursors with Dioxygen

The active site of hemerythrin as determined by x-ray absorption fine structure

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