Carbon monoxide- and oxygen-reacting haemoproteins in the mitochondrial fraction from the soil amoeba Acanthamoeba castellanii. Studies at subzero temperatures

1. Mitochondria-enriched fractions of the soil amoeba Acanthamoeba castellanii contained four haemoproteins that in their reduced forms reacted with CO to give photodissociable CO complexes; these were cytochromes a 3, a 614, b- and c-type cytochromes. 2. Non-photodissociable oxygen-containing compounds were formed at temperatures between -130 and -150 degrees C after photodissociation of CO in the presence of 200 microM-O2, 3. Electron transport, indicated by the oxidation of cytochromes a + a3 and cytochrome c, did not occur until the temperature was raised to -80 degrees C.

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Carbon monoxide-reacting haemoproteins in the mitochondrial fraction of Acanthamoeba castellanii

Biochemical Journal ◽

10.1042/bj1860669 ◽

1980 ◽

Vol 186 (3) ◽

pp. 669-678 ◽

Cited By ~ 3

Author(s):

S W Edwards ◽

D Lloyd

Keyword(s):

Carbon Monoxide ◽

Low Temperature ◽

Room Temperature ◽

Acanthamoeba Castellanii ◽

Mitochondrial Fraction ◽

Submitochondrial Particles ◽

Difference Spectra ◽

Intact Cells ◽

Mitochondrial Fractions ◽

Eukaryotic Organisms

1. Room-temperature (18 degrees C) CO difference spectra of mitochondrial fractions from the amoeba Acanthamoeba castellanii reveal the presence of at least four CO-reacting haemoproteins. As well as cytochrome a3, other components reacting with CO are: (i) a c-type cytochrome; (ii) a b-type cytochrome; and (iii) another a-type cytochrome. 2. The same components can be identified in low-temperature photodissociation experiments with intact cells or mitochondria. 3. The time of exposure to CO and the nature of the reductant are both important in identifying all the components present, in that the b-type cytochrome is more readily distinguished after longer exposure to CO and more of the c-type cytochrome is detectable when NADH is the reductant 4. Treatment of mitochondria with ultrasound releases two components, identifiable in low-temperature difference spectra as a c-type and a b-type cytochrome; only the latter appears to have any reaction with CO, and the CO-reacting c-type cytochrome is retained in submitochondrial particles. 5. The complexity of the CO-reacting haemoproteins in this organism is compared with the simpler systems found in other eukaryotic organisms.

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Oxygen affinity of the respiratory chain of Acanthamoeba castellanii

Biochemical Journal ◽

10.1042/bj2140047 ◽

1983 ◽

Vol 214 (1) ◽

pp. 47-51 ◽

Cited By ~ 15

Author(s):

D Lloyd ◽

H Mellor ◽

J L Williams

Keyword(s):

Plasma Membrane ◽

Cytochrome C ◽

Cytochrome B ◽

Respiratory Chain ◽

Oxygen Affinity ◽

Acanthamoeba Castellanii ◽

Intact Cells ◽

Cytochrome Aa3 ◽

Isolated Mitochondria ◽

Soil Amoeba

Apparent Km values for O2 for the soil amoeba Acanthamoeba castellanii determined polarographically and by bioluminescence gave similar values (0.37 and 0.41 microM respectively). Mitochondria oxidizing succinate or NADH in the presence or absence of ADP gave values in the range 0.21-0.36 microM-O2. Oxidation of respiratory-chain components to 50% of the aerobic steady states in intact cells was observed at the following O2 concentrations: cytochrome aa3, 0.1-0.25 microM; cytochrome c, 0.3-0.6 microM; cytochrome b, 0.35-0.45 microM; flavoprotein, 2 microM. In isolated mitochondria corresponding values for a-, c- and b-type cytochromes were 0.007, 0.035-0.05 and 0.06-0.09 microM-O2. It is concluded that an O2 gradient exists between plasma membrane and mitochondria in A. castellanii.

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Flavin Interaction in NADPH-Sulfite Reductase

Zeitschrift für Naturforschung B ◽

10.1515/znb-1972-0929 ◽

1972 ◽

Vol 27 (9) ◽

pp. 1087-1089 ◽

Cited By ~ 32

Author(s):

Lewis M. Siegel ◽

Edward J. Faeder ◽

Henry Kamin

Keyword(s):

Electron Transfer ◽

Electron Transport ◽

Cytochrome C ◽

Ammonium Sulfate ◽

Electron Transport Chain ◽

Sulfite Reductase ◽

E Coli ◽

Transport Chain ◽

Step Down ◽

Reduced Forms

E. coli NADPH-sulfite reductase, depleted of FMN but retaining its FAD, has been prepared by photoirradiation of native enzyme in 30% — saturated ammonium sulfate. FMN-depleted enzyme loses its ability to reduce (using NADPH) ferricyanide, cytochrome c, sulfite, or the enzyme’s own heme-like chromophore. However, the FAD remains rapidly reducible by NADPH, and the FMN-depleted enzyme retains NADPH-acetylpyridine NADP* transhydrogenase activity. Thus, FAD can serve as entry port for NADPH electrons, and FMN is required for further transmission along the enzyme’s electron transport chain. These data, plus other studies, have enabled us to suggest a mechanism for catalysis which involves FAD cycling between the fully-oxidized and fully-reduced forms while FMN cycles between fully-reduced and semiquinone. This mechanism, which includes a disproportionation step, permits a “step-down” from the twoelectron donor, NADPH, to a succession of equipotential one-electron transfer steps.

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PATHWAYS OF TERMINAL RESPIRATION IN MARINE INVERTEBRATES

The Journal of General Physiology ◽

10.1085/jgp.42.6.1185 ◽

1959 ◽

Vol 42 (6) ◽

pp. 1185-1205 ◽

Cited By ~ 17

Author(s):

F. Ghiretti ◽

Anna Ghiretti-Magaldi ◽

Luisa Tosi

Keyword(s):

Carbon Monoxide ◽

Cytochrome C ◽

Cytochrome Oxidase ◽

Succinic Dehydrogenase ◽

Chemical Properties ◽

Spectrophotometric Study ◽

Difference Spectra ◽

Respiratory Enzymes ◽

Absorption Bands ◽

Reduced Forms

The classic spectrophotometric method for identification and characterization of respiratory enzymes has been used for the study of the cytochrome system of Aplysia. Particles have been prepared from the buccal mass and the gizzard muscles. Difference spectra taken on isolated particle suspensions show the presence of a complete cytochrome system composed of five components: cytochrome a, b, c, c1, and a3. As indicated by the peaks of the sharp absorption bands of their reduced forms, they are very similar to the cytochromes of mammals and yeast. Cytochrome a3 has been identified as the terminal oxidase of Aplysia muscle by means of the spectrophotometric study of its carbon monoxide compound. Further evidence for the presence of a cytochrome system in Aplysia was obtained by assays of the catalytic activities of the isolated particles: succinic dehydrogenase, cytochrome oxidase, DPNH cytochrome c reductase. The cytochrome oxidase activity was strongly inhibited by carbon monoxide in the dark; the inhibition was totally relieved by light. Cytochrome c has been extracted and purified from muscle tissue. Its spectrum is almost identical with that of the mammalian pigment both in the oxidized and reduced forms. From the hepatopancreas a new respiratory enzyme has been extracted which has many physical and chemical properties in common with cytochrome h from terrestrial snails.

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