Ferricytochrome c and

This enzyme [EC 1.9.3.1] (also referred to as cytochrome cytochrome oxidase) catalyzes the reaction of four ferrocytochrome c with dioxygen to produce four ferricytochrome c and two water molecules. This protein also contains copper ions as cofactors. 

Nitrite reductase (NAD(P)H) [EC 1.6.6.4] catalyzes the reaction of three NAD(P)H with nitrite to yield three NAD(P)+, NH4OH, and water. Cofactors for this enzyme include FAD, non-heme iron, and siroheme. (2) Nitrite reductase (cytochrome) [EC 1.7.2.1] is a copper-depen-dent system that catalyzes the reaction of nitric oxide with two ferricytochrome c and water to produce nitrite and two ferrocytochrome c. (3) Ferredoxin-nitrite reductase [EC 1.7.7.1], a heme- and iron-dependent enzyme, catalyzes the reaction of ammonia with three oxidized ferredoxin to produce nitrite and three reduced ferredoxin. (4) Nitrite reductase [EC 1.7.99.3] is a copper- and FAD-dependent enzyme that catalyzes the reaction of two nitric oxide with an acceptor substrate and two water to produce two nitrite and the reduced acceptor. 

This enzyme [EC 1.8.2.1] catalyzes the reaction of sulfite with two ferricytochrome c and water to produce sulfate... 

The NMR investigations involved studies of the spectra of ferro-cytochrom.es c, ferricytochromes c, and the complexes with cyanide ion. For the interpretation of the data it was particularly important that methionine is the only potential hemochrome-forming amino acid which contains a methyl group. Since some of the arguments used might also apply to NMR studies of metal-ion coordination in other biological molecules a rather detailed account of these experiments is presented. 

The hyperfine shifts in the NMR spectra of ferricytochrome c and its cyanide complex (Horecker and Kornberg (43)) are markedly different (110), so that the complex formation can be observed in the NMR spectrum (Fig. 28). It is found that a 1 1 complex is formed. 

From temperature studies similar to that described for cyanoferri-myoglobin (Figs. 15 and 16) the ring current-shifted high field resonances of ferricytochrome c and cyanoferricytochrome were identified (110,111). The methionyl resonances between 1.9 and 3.7 ppm were not observed for either of the ferric compounds. This was to be expected, since in ferricytochrome c these lines are further shifted by hyperfine interactions, and in cyanoferricytochrome c the methionine is no longer one of the axial ligands. 

In Starkeya novella, sulfite is oxidized to sulfate by the catalysis of sulfite-cytochrome c oxidoreductase [reaction (4.5)]. The enzyme catalyzes the reduction with sulfite of not only native ferricytochrome c-550 but also horse ferricytochrome c and ferricyanide (Charles and Suzuki, 1966b Yamanaka et al., 1971, 1981b). The enzyme with a molecular mass of 40 kDa has a cytochrome c-551 subunit (23 kDa) (Yamanaka et al., 1981b) and molybdenum (Toghrol and Southerland, 1983). Recently, Kappler et al. (2000) has reported that the molecular mass of the enzyme is 46 kDa and has cytochrome c subunit of 8.8 kDa. 

Erman, Calorimetric studies on the interaction of horse ferricytochrome-C and yeast cytochrome-C peroxidase, Biochemistry 1995, 34, 8398-8405. 

Recently, the superoxide dismutase activity of low molecular mass copper chelates in the indirect coupled assay systems has been dispute It was demonstrated that copper in CuSO and Cu(II)(gly)2 prevents the ferricytochrome c and nitroblue tetrazolium reduction. This is not virtually new, as it is a well known phenomenon that Cu(II)-salts lead to a reoxidation of ferrocytochrome c and that they are potent inhibitors of xanthine oxidase which is often used as Oj" -generator in indirect SOD assay systems Although the indirect assays may be sometimes inadequate for the measurement of the SOD-activity, there are no doubts that low molecular mass copper chelates have their superoxide dismutase during pulse radiolysis. 

Day et al. (19676) have presented polarized crystal spectra of the low-spin compounds ferricytochrome c and ferrimyoglobin cyanide. In both spectra a weak band at about 8000 cm" was found to be polarized in the heme plane. Ferricytochrome c also displays another band at 10,700 cmwhich probably indicates that the heme complex contains a few percent of the high-spin form since such a band is found in this region in high-spin ferric hemoproteins. 

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