Hemerythrin dioxygen binding

Detailed kinetic and mechanistic studies were performed in order to determine the mechanism of dioxygen binding to hemerythrin at the molecular level, and quantum... 

FIGURE 4.5 Proposed mechanism of dioxygen binding by hemerythrin.17... 

Few dinuclear iron(II) complexes are known where the ligands approximately resemble those believed or known to occur in the family of t-oxodi-iron(III) proteins. The dioxygen-binding process in hemerythrin has no close nonbiological analogue. Although spectroscopically similar to oxyhemerythrin. 

The common thread that relates hemerythrin, MMO, and ribonucleotide reductase is the involvement of dioxygen with a diiron active site. For hemerythrin, reversible dioxygen binding is its function and much is known of this chemistry. For MMO and ribonucleotide reductase, the role of dioxygen and its mechanism of activation is just beginning to emerge. 

Figure 16. Proposed mechanism for reversible dioxygen binding in hemerythrin. Adapted from Ref. 2.

Hemerythrin, deoxy-dioxygen binding, 689 Hemiporphyrazines metal complexes dyes, 91... 

The di-iron site and formulation of the 02-binding reaction Mechanism of dioxygen binding Autoxidation Cooperative hemerythrins Mixed-valent forms Synthetic models... 

Proton-coupled electron transfer (PCET) is known to play an important role in a variety of biological processes, including microbial iron transport by ferric enterobactin, enzyme catalysis in systems such as fumarate reductase and nitrate reducatase, and dioxygen binding by the non-heme iron protein hemerythrin. " As such, pH-dependent electrochemical studies can play an important role in unraveling these mechanisms. The most heavily studied biological system known to involve PCET is cytochrome c oxidase, the terminal electron-transfer complex of the mitochondrial respiratory chain, which catalyzes the reduction of molecular oxygen to water. ... 

Earlier EPR studies were also extended to the nitrosyl adducts of deoxyhe-merythrin since the NO adduct is believed to be a reasonable mimic of the superoxide intermediate expected to be formed upon reaction of hemerythrin wifli O2 [92,93,95,526] The spin-Hamiltonian parameters for the Fe - FeNO unit of NO-deoxyhmerythrin are consistent with antiferromagnetic coupling between the two iron centers, and the coordination of NO to the five-coordinate Fe2, as expected for dioxygen binding. 

Brunold TC, Solomon EL 1999. Reversible dioxygen binding to hemerythrin, 1 electronic structures of deoxy- and oxyhemerythrin. J Am Chem Soc 121 8277-8287. 

Bumold, T. C., 8c Solomon, E. I. (1999). Reversible dioxygen binding to hemerythrin. Journal of the American Chemical Society, 121, 8288. 

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