Heme proteins cytochromes

Cytochrome ala (a Cu/heme protein cytochrome oxidase, complex IV) transfers electrons to oxygen... 

The enzyme cytochrome c oxidase ( COX, EC 1.93.1) catalyzes the final step of the respiratory chain. It receives electrons from the small heme protein cytochrome c and transfers them to molecular oxygen, which is thereby reduced to water (see p. 140). At the same time, 2-4 protons per water molecule formed are pumped from the matrix into the intermembrane space. 

Because of their structural and spectroscopic analogies with the hemo-chromes Fe(P)L2, e.g. the protoporphyrin derivative 3 (L, L = Py or 1-Meim), the corresponding 4d and 5d homologs are named ruthenochromes or osmo-chromes . The hemochromes derive their name from the cytochromes, the widespread electron-carrying heme proteins. Cytochrome b (coordination type F, M = Fe) has two imidazole donors from histidine side chains at the central iron, cytochrome c (coordination type G, M = Fe) an imidazole and a methyl-thioether function from a methionine. F is an axially symmetrical, G an axially unsymmetrical system. 

The mechanism in hepatic cellular metabolism involves an electron transport system that functions for many drugs and chemical substances. These reactions include O-demethylation, N-demethyla-tion, hydroxylation, nitro reduction and other classical biotransformations. The electron transport system contains the heme protein, cytochrome P-450 that is reduced by NADPH via a flavoprotein, cytochrome P-450 reductase. For oxidative metabolic reactions, cytochrome P-450, in its reduced state (Fe 2), incorporates one atom of oxygen into the drug substrate and another into water. Many metabolic reductive reactions also utilize this system. In addition, there is a lipid component, phosphatidylcholine, which is associated with the electron transport and is an obligatory requirement for... 

Heme proteins (cytochromes) Iron-sulfur centers Other non-heme iron0... 

The mass of protein containing one gram atom of iron is 13,145 g, which therefore represents the molar mass of the protein. The minimum molecular weight is thus 13,145. This is close to the molecular weight of the heme protein cytochrome c, and is thus a reasonable value. However, had the molecule of protein contained more than one atom of iron, the molecular weight would have been a multiple of 13,145. 

Comparative Studies of Resting State Active Sites of Four Heme Proteins. In this second type of study reported, we have used the x-ray structure of the active site of four heme proteins cytochrome... 

This section firstly includes discussion of the NMR properties of certain paramagnetic porphyrins and is then concerned with recent developments in the study of the heme proteins cytochrome c and myoglobin, both of which comprise single polypeptide chains to which a protoporphyrin IX is bound, and hemoglobin which consists of four subunit heme polypeptides. 

Raffalt, A.C., Schmidt, L., Christensen, H.E.M., Chi, Q., and Ulstrup, J. (2009) Electron transfer patterns of the di-heme protein cytochrome c(4) from Pseudomonas stutzeri. Journal of Inorganic Biochemistry, 103, 717-722. 

Yeasts, via oxidases acting as dehydrogenases (D-glucose oxidase), produce substantial fluxes of HOOH. In order to "harvest" the redox energy of this intermediate, these organisms have a heme protein (cytochrome-c peroxidase) to facilitate the electron-transfer oxidation of two cytochrome c-[Fe(II)] molecules... 

There are 32 microscopic formal potentials for the redox process of the tetra-heme protein, cytochrome C3, and the deconvolution of these microscopic states distributed over 110 mV is impossible using electrochemical techniques. Many heme-methyl signals are observed separately, e.g. each heme of cytochrome C3 has four methyl groups so that 80 three-proton intensity signals originating from the 16 heme-methyl groups would be expected in the course of a four-electron reduction process. The microscopic formal potentials of the 32 redox processes can be calculated from the chemical shifts of each heme-methyl group at the five macroscopic oxidation states [125, 127]. The results are shown in Table 6 and the macroscopic formal potential can be deduced from these results. 

The existence of mitochondrial cytochrome P450 in adrenal cortex was reported originally by Harding et al (1964) and confirmed by subsequent studies. Adrenal cortical mitochondria catalyze a number of NADPH- and molecular-oxygen-dependent hydroxylation reactions that contribute to the biosynthesis of corticosteroids. The enzyme system for 11 jS-hydroxyla-tion has been isolated, and a successful reconstitution of its activity has been achieved by the interaction of three proteins, namely an NADPH-dependent flavoprotein (adrenodoxin reductase), an iron-sulfur protein (adrenodoxin), and the heme protein (cytochrome P450) that serves as the terminal oxidase for the electron transport system from NADPH to oxygen (Wang and... 

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