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PubMed1998

Cofactor engineering: a novel approach to metabolic engineering in Lactococcus lactis by controlled expression of NADH oxidase.

NADH oxidase-overproducing Lactococcus lactis strains were constructed by cloning the Streptococcus mutans nox-2 gene, which encodes the H2O-forming NADH oxidase, on the plasmid vector pNZ8020 under the control of the L. lactis nisA promoter. This engineered system allowed a nisin-controlled 150-fold overproduction of NADH oxidase at pH 7.0, resulting in decreased NADH/NAD ratios under aerobic conditions. Deliberate variations on NADH oxidase activity provoked a shift from homolactic to mixed-acid fermentation during aerobic glucose catabolism. The magnitude of this shift was directly dependent on the level of NADH oxidase overproduced. At an initial growth pH of 6.0, smaller amounts of nisin were required to optimize NADH oxidase overproduction, but maximum NADH oxidase activity was twofold lower than that found at pH 7.0. Nonetheless at the highest induction levels, levels of pyruvate flux redistribution were almost identical at both initial pH values. Pyruvate was mostly converted to acetoin or diacetyl via alpha-acetolactate synthase instead of lactate and was not converted to acetate due to flux limitation through pyruvate dehydrogenase. The activity of the overproduced NADH oxidase could be increased with exogenously added flavin adenine dinucleotide. Under these conditions, lactate production was completely absent. Lactate dehydrogenase remained active under all conditions, indicating that the observed metabolic effects were only due to removal of the reduced cofactor. These results indicate that the observed shift from homolactic to mixed-acid fermentation under aerobic conditions is mainly modulated by the level of NADH oxidation resulting in low NADH/NAD+ ratios in the cells.

Acetoin↗
PubMed1965

COMPARISION OF SOLUBLE REDUCED NICOTINAMIDE ADENINE DINUCLEOTIDE OXIDASES FROM CELLS AND SPORES OF CLOSTRIDIUM BOTULINUM.

Green, J. H. (Michigan State University, East Lansing), and H. L. Sadoff. Comparison of soluble reduced nicotinamide adenine dinucleotide oxidases from cells and spores of Clostridium botulinum. J. Bacteriol. 89:1499-1505. 1965.-The properties of purified reduced nicotinamide adenine dinucleotide (NADH(2)) oxidases from cells and spores of Clostridium botulinum 62-A have been studied to determine whether they are the same or different proteins. The spore NADH(2) oxidase was very heat-stable, whereas the vegetative enzyme was readily denatured at 70 C. The spore oxidase exhibited less affinity for the substrate than did the vegetative protein, but possessed a tightly bound cofactor. Atabrine was a noncompetitive inhibitor for both enzymes, but was less inhibitory to the spore NADH(2) oxidase. The enzymes could be separated from each other by gel filtration or chromatography on a diethylaminoethyl-cellulose column. The molecular weight of the spore oxidase was estimated to be 200,000 or greater, whereas that of the vegetative enzyme was 100,000 or less. Neither NADH(2) oxidase would cross-react with its heterologous antibody in a precipitation reaction. The conclusion drawn from this investigation is that the two NADH(2) oxidases are distinctly different proteins.

Bacterial Proteins↗
PubMed1989

Immunological identification of the alternative oxidase of Neurospora crassa mitochondria.

Neurospora crassa mitochondria use a branched electron transport system in which one branch is a conventional cytochrome system and the other is an alternative cyanide-resistant, hydroxamic acid-sensitive oxidase that is induced when the cytochrome system is impaired. We used a monoclonal antibody to the alternative oxidase of the higher plant Sauromatum guttatum to identify a similar set of related polypeptides (Mr, 36,500 and 37,000) that was associated with the alternative oxidase activity of N. crassa mitochondria. These polypeptides were not present constitutively in the mitochondria of a wild-type N. crassa strain, but were produced in high amounts under conditions that induced alternative oxidase activity. Under the same conditions, mutants in the aod-1 gene, with one exception, produced apparently inactive alternative oxidase polypeptides, whereas mutants in the aod-2 gene failed to produce these polypeptides. The latter findings support the hypothesis that aod-1 is a structural gene for the alternative oxidase and that the aod-2 gene encodes a component that is required for induction of alternative oxidase activity. Finally, our results indicate that the alternative oxidase is highly conserved, even between plant and fungal species.

Antibodies, Monoclonal↗
PubMed1992

Rapid cytochemical demonstration of cytochrome oxidase activity in pathogenic bacteria.

AIMS: To develop and assess a cytochemical technique for the light microscopical detection of oxidase activity in pathogenic bacteria. METHODS: Live bacterial cells were deposited on to aminopropylsilane treated glass coverslips by centrifugation, dried, then reacted with either 1% (w:v) n,n,n',n'-tetramethyl-p-phenylene diamine (TPD) or 5 mM diaminobenzidine (DAB) at 37 degrees C. The preparations were mounted in 50% glycerol and assessed by brightfield microscopy. An optimised DAB procedure (5 minutes of drying at 37 degrees C and 10 minutes of reaction time) was applied to 44 strains of organisms commonly associated with infections in man and to two fresh positive blood culture containing Gram negative bacilli. RESULTS: TPD gave no discernible localised reaction product and was not investigated further. With DAB, oxidase positive cells (brown) were clearly differentiated from oxidase negative cells (colourless) even in mixed preparations. The DAB technique correctly assigned 18 oxidase positive isolates (seven genera), 26 oxidase negative isolates (eight genera), and the organisms present in the two freshly positive blood cultures to their appropriate oxidase reactivity as defined by the standard macroscopic TPD technique. CONCLUSIONS: The cytochemical reaction seems to be a reliable indicator of the macroscopic oxidase test. It permits determination of oxidase reactivity at an early stage in the assessment of clinical material when infecting organisms can be demonstrated by microscopy. Further development of this and related cytochemical techniques could permit the provision of microbiological information that would be relevant to patient management, well in advance of conventional techniques.

3,3'-Diaminobenzidine↗
PubMed1994

Acute disruption of cytochrome oxidase activity in brain in a perinatal rat stroke model.

Cytochrome oxidase histochemistry in frozen brain sections provides an estimate of mitochondrial respiratory function and neuronal metabolic activity. We hypothesized that in a perinatal rodent stroke model acute selective disruption of cytochrome oxidase activity could identify neuronal populations susceptible to irreversible ischemic injury. In 7-d-old rats, focal ischemic injury was induced by right carotid ligation followed by 8% O2 exposure (2.75 h); this procedure elicits ipsilateral forebrain injury with prominent hippocampal lesions, often including dentate gyrus. Cytochrome oxidase activity was quantitated by densitometry in brain sections prepared from animals killed 1 h (n = 8), 24 h (n = 11), or 5 d (n = 3) posthypoxia. At 1 h posthypoxia, in six of eight there was diffuse ipsilateral suppression of cytochrome oxidase activity (p = 0.0001, two-way analysis of variance, compared with values in contralateral hemisphere), which was most marked in periventricular regions including dentate gyrus (-29%), medial habenula (-38%), and posterolateral thalamic nucleus (-42%). Nissl staining of adjacent sections was completely intact in four of eight, and four of eight had subtle focal reductions in staining. At 24 h and 5 d posthypoxia, heterogeneous suppression of cytochrome oxidase activity persisted in the lesioned hemisphere, with close anatomic correspondence between loss of cytochrome oxidase activity and loss of Nissl staining. Additional studies indicated that the threshold duration of 8% O2 exposure (after carotid ligation) for suppression of cytochrome oxidase activity was 1-2 h. Disruption of cytochrome oxidase activity represents one of the earliest detectable indicators of neuronal injury in this perinatal stroke model.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1988

Estrogen induces accumulation of the mitochondrial ribonucleic acid for subunit II of cytochrome oxidase in pituitary tumor cells.

The gene for subunit II of cytochrome oxidase is part of the mitochondrial genome. 17 beta-Estradiol, 1 nM, increased the levels of cytochrome oxidase II mRNA in the GH4C1 pituitary tumor cell line; the increases ranged from 3- to 16-fold over controls in different experiments. Insulin, 300 nM, estradiol, 1 nM, and epidermal growth factor, 10 nM, together caused a larger increase in cytochrome oxidase II mRNA accumulation than did estradiol alone. The dose-response relationship for the induction of cytochrome oxidase II mRNA by estradiol was similar to that for PRL mRNA; maximal induction occurred at about 10(-9) M. This concentration is 10-fold greater than that required for maximal stimulation of cell proliferation and of 1C28, another estrogen-inducible mRNA, indicating that the increase in cytochrome oxidase II mRNA is not a result of increasing the growth rate of the cells. The increase in cytochrome oxidase II mRNA was not caused by an increase in the number of copies of the cytochrome oxidase II gene. Estradiol therefore must induce in the mitochondria an increase in transcription or a decrease in degradation of cytochrome oxidase II mRNA.

Animals↗
PubMed1997

Further evidence for the presence of mitochondrially encoded subunits in cytochrome c oxidase of the trypanosomatid Crithidia fasciculata.

Mitochondrial mRNAs in trypanosomatids are edited by uridylate insertion and deletion. The respiratory chain complexes cytochrome c reductase, cytochrome c oxidase and F0F1-ATPase of the insect trypanosomatid Crithidia fasciculata have been isolated and analysed by peptide microsequencing, but so far, proteins encoded by edited (and unedited) mitochondrial mRNAs have not been found. In this paper, we provide evidence that the mitochondrial mRNAs encoding the three large subunits of cytochrome c oxidase are indeed translated. First, purified holo cytochrome c oxidase turned out to be cysteine-rich, in agreement with the high cysteine codon-content of the sequence of mitochondrial cox subunit mRNAs. Second, in mass spectrometry measurements of cytochrome c oxidase, a protein was detected with the predicted molecular weight of cytochrome c oxidase subunit 2. Finally, an antibody generated against a fusion protein produced in Escherichia coli from constructs containing a segment of cytochrome c oxidase subunit 2 cDNA, specifically recognised protein bands present in cytochrome c oxidase following SDS PAGE. However, these proteins were present in the high molecular weight region of the gel, suggesting that cytochrome c oxidase subunit 2 aggregates in the presence of SDS.

Animals↗
PubMedDate not supplied

Photoinactivation and protection of glycolate oxidase in vitro and in leaves.

Glycolate oxidase that was partially purified from pea leaves was inactivated in vitro by blue light in the presence of FMN. Inactivation was greatly retarded in the absence of O2. Under aerobic conditions H2O2 was formed. The presence of catalase, GSH or dithiothreitol protected glycolate oxidase against photoinactivation. Less efficient protection was provided by ascorbate, histidine, tryptophan or EDTA. The presence of superoxide dismutase or of hydroxyl radical scavengers had no, or only minor, effects. Glutathione suppressed H2O2 accumulation and was oxidized in the presence of glycolate oxidase in blue light. Glycolate oxidase was also inactivated in the presence of a superoxide-generating system or by H2O2 in darkness. In intact leaves photoinactivation of glycolate oxidase was not observed. However, when catalase was inactivated by the application of 3-amino-1,2,4-triazole or depleted by prolonged exposure to cycloheximide a strong photoinactivation of glycolate oxidase was also seen in leaves. In vivo blue and red light were similarly effective. Furthermore, glycolate oxidase was photoinactivated in leaves when the endogenous GSH was depleted by the application of buthionine sulfoximine. Both catalase and antioxidants, in particular GSH, appear to be essential for the protection of glycolate oxidase in the peroxisomes in vivo.

Aerobiosis↗
PubMed1992

Homology in the structure and the prosthetic groups between two different terminal ubiquinol oxidases, cytochrome a1 and cytochrome o, of Acetobacter aceti.

Acetobacter aceti produces two different terminal oxidases dependent on the culture conditions, shaking and static cultures. Cells grown on shaking culture contain cytochrome a1, while cytochrome o is present in cells grown on static culture. Cytochrome a1 and cytochrome o of A. aceti were compared especially with respect to the protein structure and the prosthetic groups. Cytochrome a1 exhibited lower CN sensitivity and higher affinity for O2 than cytochrome o. Both terminal oxidases consisted of four nonidentical polypeptides of which the molecular sizes were identical between both enzymes. Cytochrome a1 cross-reacted with an antibody raised against cytochrome o at the same level as cytochrome o did, and an antibody elicited against cytochrome a1 cross-reacted with both cytochrome o and cytochrome a1 at the same intensity, which indicates that both oxidases are indistinguishable immunochemically. Furthermore, almost the same peptide mapping pattern with chymotrypsin was observed in subunit I and in subunit II between both terminal oxidases, and the amino-terminal sequences in the subunit II of both oxidases were identical at least in their 10 amino acids. As for the prosthetic groups, both oxidases were shown to contain two heme-irons and one copper atom. Further, high performance liquid chromatography analysis of the heme moieties extracted from both the purified enzymes indicated that cytochrome a1 contains hemes b and a at a ratio of 1 to 1, whereas cytochrome o contains the same amounts of hemes b and o. Thus, data indicate that cytochrome a1 and cytochrome o of A. aceti are cytochrome ba and cytochrome bo ubiquinol oxidases, respectively, and that both oxidases have a closely similar protein structure and prosthetic groups, in which only heme a in the heme/copper binuclear center of cytochrome a1 is replaced by heme o in that of cytochrome o.

Acetobacter↗
PubMed1977

Tryptic cleavage of rat liver sulfite oxidase. Isolation and characterization of molybdenum and heme domains.

Treatment of rat liver sulfite oxidase with trypsin leads to loss of ability to oxidize sulfite in the presence of cytochrome c as electron acceptor. Ability to oxidize sulfite with ferricyanide as acceptor is undiminished, while sulfite leads to O2 activity is partially retained. Gel filtration of the proteolytic products has led to the isolation of two major fragments of dissimilar size derived from sulfite oxidase. The smaller fragment has a molecular weight of 9500 and appears to be monomeric when detached from sulfite oxidase. It contains the heme in its cytochrome b5 structure, has no sulfite oxidase activity, and is reducible with dithionite but not with sulfite. The heme fragment can mediate electron transfer between pig liver microsomal NADH cytochrome b5 reductase and cytochrome c. The larger fragment has a molecular weight of 47,400 under denaturing conditions but elutes from Sephadex G-200 as a dimer. It contains no heme but retains all of the molybdenum and the modified sulfite-oxidizing capacity present in the proteolytic mixture. All of the EPR properties of the molybdenum center of native sulfite oxidase are retained in the molybdenum fragment. The molybdenum center is a weak chromophore with an absorption sectrum suggestive of coordination with sulfur ligands. Reduction by sulfite generates a spectrum attributable to molybdenum (V). Spectra of oxidized and sulfite-reduced preparations are sensitive to anions and pH. NH2-terminal analysis of native sulfite oxidase and the two tryptic fragments has permitted the conclusion that the sequence represented by the heme fragment is the NH2 terminus of native enzyme. These studies have demonstrated that the two cofactor moieties of sulfite oxidase are contained in distinct domains which are covalently held in contiguity by means of an exposed hinge region. Isolation of functional heme and molybdenum domains of sulfite oxidase after tryptic cleavage has demonstrated conclusively that the cytochrome b5 region of the molecule is required for electron transfer to the physiological acceptor, cytochrome c.

Animals↗
PubMed1975

Functional intermediates in the reaction of membrane-bound cytochrome oxidase with oxygen.

Flash photolysis of the membrane-bound cytochrome oxidase/carbon monoxide compound in the presence of oxygen at low temperatures and in the frozen state leads to the formation of three types of intermediates functional in electron transfer in cytochrome oxidase and reduction of oxygen by cytochrome oxidase. The first category (A) does not involve electron transfer to oxygen between -125 degrees and -105 degrees, and includes oxy compounds which are spectroscopically similar for the completely reduced oxidase (Cu1+alpha3(2+)-O2) or for the ferricyanide-pretreated oxidase (Cu2+alpha3(3+)-O2). Oxygen is readily dissociated from compounds of type A. The second category (B) involves oxidation of the heme and the copper moiety of the reduced oxidase to form a peroxy compound (Cu2+alpha 3(3+)-O2=or Cu2+alpha3(2+)-O2H2) in the temperature range from -105 degrees to -60 degrees. Above -60 degrees, compounds of type B serve as effective electron acceptors from cytochromes a, c, and c1. The third category (C) is formed above -100 degrees from mixed valency states of the oxidase obtained by ferricyanide pretreatment, and may involve higher valency states of the heme iron (Cu2+alpha3(4+)-O2=). These compounds act as electron acceptors for the respiratory chain and as functional intermediates in oxygen reduction. The remarkable features of cytochrome oxidase are its highly dissociable "oxy" compound and its extremely effective electron donor reaction which converts this rapidly to tightly bound reduced oxygen and oxidized oxidase.

Animals↗
PubMed1976

Reconstitution of biological molecular generators of electric current. Cytochrome oxidase.

1. Direct measurement of the electric current generation by cytochrome oxidase has been carried out. To this end, two procedures were used. The simpler one consists in formation of planar artificial membrane from the mixture of decane solution of soya bean phospholipids and beef heart cytochrome oxidase. Addition of cytochrome c and ascorbate to one of the two compartments separated by the cytochrome oxidase-containing planar membrane was found to result in a transmembrane electric potential difference being formed (plus on cytochrome c side of the membrane). Maximal values of potential differences obtained by this method were about 40 mV. Much higher potentials were observed when another ("photeoliposome-planar membrane") method was applied. In this case cytochrome oxidase was reconstituted with phospholipid to form proteoliposomes which adhered to planar phospholipid membrane in the presence of Ca2+ ions. Addition of cytochrome c and ascorbate to the proteoliposome-containing compartment gives rise to generation of an electric potential difference across the planar membrane, which reached 100 mV at a current of about 1 X 10(-11) A (minus in the proteoliposome-free compartment). The electromotive force of this generator was estimated as being about 0.2 V. If ascorbate and proteoliposomes were added into different compartments, a penetrating hydrogen atom carrier (phenazine methosulfate, (PMS) or tetramethyl-p-phenylenediamine (TMPD)) was required for a membrane potential to be formed. Generation of an electric potential difference of the opposite direction (plus in the proteoliposome-free compartment) was revealed in experiments with cytochrome oxidase proteoliposome containing cytochrome c in their interior. In this case, addition of PMS or TMPD was necessary. 2. In the suspension of cytochrome oxidase proteoliposome the uptake of a cationic penetrant (tetraphenyl phosphonium cation) was found to be coupled with electron transfer via external cytochrome c. Electron transfer via intraproteoliposomal cytochrome c induced the uptake of anionic penetrants (tetraphenyl borate and phenyldicarbaundecaborane anions). 3. All the above effects were sensitive to cyanide and protonophorous uncouplers. 4. In proteoliposomes containing both cytochrome oxidase and bacteriorhodopsin, the light- and oxidation-dependent generations of membrane potential have been revealed. 5. The data obtained are in agreement with Mitchell's idea of transmembrane electron flow in the cytochrome oxidase segment of the respiratory chain.

Animals↗
PubMed1990

[Aerobic metabolism of VX and mixed function oxidases].

In our preliminary study, it has been found that VX oxidase exists in the microsome fraction of rat liver and the catalytic reaction needs the participation of molecular oxygen and coenzyme I or II. In this paper, the data showed that deoxycholate inactivated both the mixed function oxidase and VX oxidase. The specific inhibitor proadifen of the mixed function oxidase also profoundly inhibited VX oxidase activity. The complex of VX and cytochrome P-450 exhibited typical difference spectrum of type I. Aniline competitively inhibited the inactivation of VX catalyzed by microsomes. These results indicate that VX is one of the substrates of mixed function oxidase. VX oxidase in the rat liver cells is exactly the mixed function oxidase.

Aerobiosis↗
PubMed1988

[Effect of hydrazine on properties of cytochrome oxidase].

The effects of hydrazine on ferrocytochrome c oxidation by cytochrome oxidase and on spectral properties of the enzyme were studied. Hydrazine was found to modify the spectral properties of lipid-depleted preparations of cytochrome oxidase dissolved in 1% cholate and to inhibit the cytochrome c oxidase activity of the enzyme, whereas the kinetic properties of lipid-enriched and Tween preparations were unchanged by hydrazine. Cytochrome oxidase was found to possess a hydrazine oxidase activity. This activity was not coupled with the specific cytochrome c oxidase activity. The effect of pH on the observed changes was studied. Hydrazine was found to yield protein bands in the optical spectra of cytochrome oxidase as 580 nm, 537 nm and 845 nm. It is concluded that hydrazine interacts with the oxygen-binding site of cytochrome oxidase. The effect of hydrazine on the formation of the "ferryl" form (Fe4+a3/Cu2+b) of the enzyme is discussed.

Animals↗
PubMed1986

Nuclear genes for cytochrome c oxidase subunits of Neurospora crassa. Isolation and characterization of cDNA clones for subunits IV, V, VI, and possibly VII.

We obtained cDNA clones for cytochrome oxidase subunits IV, V, VI, and possibly VII by constructing a lambda gt11 library of Neurospora crassa cDNA and probing it with antiserum directed against Neurospora cytochrome oxidase holoenzyme. Positive clones were further characterized with antisera directed against individual cytochrome oxidase subunits and subsequently by DNA sequencing. The clones for subunits IV and V encode proteins with regions matching the known N-terminal amino acid sequences of purified Neurospora cytochrome oxidase subunits IV and V, respectively. The sequences of these clones provide the first evidence that cytochrome oxidase subunits IV and V are made as precursors with N-terminal extensions in Neurospora. The N-terminal extensions encoded by these clones share homology, and are rich in arginine, as are signal sequences of other mitochondrially destined proteins. The subunit VI clone codes for the carboxyl terminus of a protein homologous to the carboxy termini of yeast cytochrome oxidase subunit VI and bovine cytochrome oxidase subunit Va. The subunit VII clone contains an open reading frame for a 47-residue protein, the expected size for subunit VII. However, the protein coded by this clone has an unusual amino acid composition. Whether this clone represents an authentic cytochrome oxidase subunit is not established.

Amino Acid Sequence↗
PubMed1986

Nuclear functions required for cytochrome c oxidase biogenesis in Saccharomyces cerevisiae. Characterization of mutants in 34 complementation groups.

To identify nuclear functions required for cytochrome c oxidase biogenesis in yeast, recessive nuclear mutants that are deficient in cytochrome c oxidase were characterized. In complementation studies, 55 independently isolated mutants were placed into 34 complementation groups. Analysis of the content of cytochrome c oxidase subunits in each mutant permitted the definition of three phenotypic classes. One class contains three complementation groups whose strains carry mutations in the COX4, COX5a, or COX9 genes. These genes encode subunits IV, Va, and VIIa of cytochrome c oxidase, respectively. Mutations in each of these structural genes appear to affect the levels of the other eight subunits, albeit in different ways. A second class contains nuclear mutants that are defective in synthesis of a specific mitochondrial-encoded cytochrome c oxidase subunit (I, II, or III) or in both cytochrome c oxidase subunit I and apocytochrome b. These mutants fall into 17 complementation groups. The third class is represented by mutants in 14 complementation groups. These strains contain near normal amounts of all cytochrome c oxidase subunits examined and therefore are likely to be defective at some step in holoenzyme assembly. The large number of complementation groups represented by the second and third phenotypic classes suggest that both the expression of the structural genes encoding the nine polypeptide subunits of cytochrome c oxidase and the assembly of these subunits into a functional holoenzyme require the products of many nuclear genes.

Cell Nucleus↗
PubMedDate not supplied

[Absorption spectra and magnetic circular dichroism of heme-containing proteins in nonequilibrium states. VI. Cytochrome c-oxidase].

Low temperature (77 degrees K) absorption spectra of nonequilibrium states of cytochrome c oxidase produced by reduction of oxidases form protein by thermolysed electrons at 77 degrees K was studied. During reduction of cytochrome oxidase water-glycerol solution by thermolysed electrons at 77 degrees K a nonequilibrium reduced protein is formed. Low temperature (77 degrees K) absorption spectra of the nonequilibrium cytochrome oxidase differs from those reduced by ditionite. It was shown that the oxidation state of cytochrome a3 or addition of cytochrom c have no influence on these spectral changes. It is assumed, that the observed effects are conditioned by structural differences of reduced and oxidased cytochrome oxidase active center. Similar spectral changes were observed for cytochrome oxidase, bound to the mitochondrial membrane. At temperature increasing the low temperature reduced protein is relaxed to a corresponding equilibrium state. The spectral properties of bacterial cytochrome oxidase M. lysodeicticus do not depend on the way of reduction (by dytionite or thermolysed electrons at 77 degrees K).

Animals↗
PubMed1980

Reduced cytochrome c oxidase. A new form absorbing at 443 and 603 nm.

Reduced cytochrome c oxidase is known to absorb strongly at 445 nm and 605 nm regardless of the chemical or physiological nature of the reductant. When the reduced oxidase is allowed to interact with cytochrome c3 under conditions in which there is no net change in the oxidation state of the oxidase, the absorption bands shift from those commonly found to 443 nm and 603 nm. This new oxidase form is postulated to be the intermediate in the catalytic cycle of the oxidase that results in the formation of the 418-nm form of the oxidized oxidase; it is further postulated that the 445-nm form is the intermediate in the catalytic cycle that results in the 428-nm form of the oxidized oxidase. The relevance of the 443-nm, 603-nm form to the conformational cycle of the oxidase as well as its possible involvement in energy transduction at Site II of oxidative phosphorylation are discussed.

Anaerobiosis↗