Ferroheme protein

Indolamine dioxygenase (- Tryptamine oxygen 2,3-oxidoreductase (decyclizing). This enzyme which is either a ferroheme protein which uses oxygen as dioxygen substrate or a ferriheme protein using superoxide ion 129, 130) is non-specific in its choice of substrates (2,127). 

Figure 18.4 Structures of heme/Cu oxidases at different levels of detail, (a) Position of the redox-active cofactors relative to the membrane of CcO (left, only two obligatory subunits are shown) and quinol oxidase (right), (b) Electron transfer paths in mammalian CcO. Note that the imidazoles that ligate six-coordinate heme a and the five-coordinate heme are linked by a single amino acid, which can serve as a wire for electron transfer from ferroheme a to ferriheme as. (c) The O2 reduction site of mammalian CcO the numbering of the residues corresponds to that in the crystal structure of bovine heart CcO. The subscript 3 in heme as and heme 03 signifies the heme that binds O2. The structures were generated using coordinates deposited in the Protein Data Bank, lari [Ostermeier et al., 1997] Ifft [Abramson et al., 2000] (a) and locc [Tsukihara et al., 1996] (b, c).

Both siroheme enzymes form ferroheme-NO complexes in which the g value anisotropy appears somewhat smaller than in the corresponding complexes of most other enzymes. The EPR spectra of the complexes somewhat resemble the spectra of the high-temperature myoglobin-NO complexes. The hyperfine splitting from the NO nitrogen nucleus is evident at intermediate g values but is not well resolved. These enzymes are capable of reducing NO to ammonia if supplied with low potential reducing equivalents. Other heme proteins also catalyze oxidation reduction reactions with NO. 

In hemoglobin and myoglobin the globin protein protects the ferroheme, which is tucked into a hydrophobic crevice of the protein, known as the heme pocket . 

Ferrohemoglobin, hemoglobin (reduced hemoglobin) a conjugated protein formed by combination of ferroheme and native protein. 

Ferroheme, also called heme, is iron(II) protoporphyrin, with a bipositive iron atom replacing the two central hydrogen atoms. The iron atom is located in or near the plane of the molecule, and it forms bonds with all four nitrogen atoms. Ferroheme is a constituent of hemoglobin and of some other proteins. 

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