Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies are reported on the interrelationships in liver mitochondria of copper status, cytochrome oxidase activity, adenine nucleotide binding capacity and phospholipid synthesis. Direct exposure of mitochondria to cyanide or diethyldithiocarbamate depressed cytochrome oxidase activity; ADP-binding and phospholipid synthesis. Fractionation of mitochondria to increase the specific activity of cytochrome oxidase about 10-fold did not increase the affinity to bind ADP. Ageing of mitochondria or dialysis of mitochondria or mitochondrial membrane preparations against water or diethyldithiocarbamate at 0--2 degrees for 18 h did not decrease cytochrome oxidase activity or copper content of reisolated and resuspended mitochondria or mitochondrial membrane preparations, but considerably reduced the affinity to bind ADP. The respiratory inhibitors, fluoride and azide, at concentrations inhibitory to cytochrome oxidase did not reduce ADP-binding or phospholipid synthesis. Atractyloside did not inhibit cytochrome oxidase activity but did inhibit ADP-binding and phospholipid synthesis. Pre-incubation of mitochondrial membrane preparations with Cu++ increased the copper content and ADP-binding affinity. The results indicate that cytochrome oxidase is not the ADP-binding site of the mitochondrial membrane system and that reduced cytochrome oxidase activity per se does not depress binding affinity. Copper appears to be a component of the adenine nucleotide binding sites of mitochondrial membranes because the copper-complexing agents, cyanide and diethyldithiocarbamate, depressed ADP-binding, while increased mitochondrial membrane copper content increased ADP-binding.
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PMID:Interrelationships of copper, cytochrome oxidase, phospholipid synthesis and adenine nucleotide binding. 19 61

The x-ray absorption edge spectra of the Cu and Fe-centers in oxidized and reduced cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase: EC 1.9.3.1) have been obtained using synchrotron radiation from the SPEAR storage ring at the Stanford Linear Accelerator Center. In addition, oxidized and reduced plastocyanin as well as a number of model copper compounds in various oxidation states were also examined. A comparison of the absorption edge fine structure of cytochrome oxidase with those of the models indicates that one of the two coopers in the oxidized protein is in the +1 oxidation state. Upon reduction of the protein with dithionite, the second copper becomes Cu(I). The shift in the Fe K-edge of cytochrome oxidase upon reduction is small (about 2 e V or 3 times 10(-19 J) and is comparable to that previously observed for the reduction of the heme iron of cytochrome c.
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PMID:X-ray absorption edge studies on oxidized and reduced cytochrome c oxidase. 19 7

Purified lipid-depleted cytochrome oxidase, at purity of 12--14 nmol heme a per mg protein, has been shown to contain seven non-identical subunits in the ratio of unity. Their molucular weights on polyacrylamide gel are, in thousands, 40, 21, 14.8, 13.5, 11.6, 9.5, and 7.6 from gel electrophoresis after dissociation in sodium dodecyl sulfate and beta-mercaptoethanol. The molar ratio is determined by the amino acid composition of each subunit obtained from direct hydrolysis of the stained polyacrylamide gel slices. The amino acid composition of the isolated subunits I and II determined by regular hydrolysis method is found practically the same as that from direct hydrolysis of gel slices. The heme-associated polypeptides are identified with subunits of molecular weights of 40.10(3) and 11.6.10(3). One of the two coppers associated with the polypeptide of molecular weight of 21 000. The second copper may be associated with heme in the subunit of 40.10(3). Evidence of the existence of interpolypeptide disulfide linkages is presented.
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PMID:Identification of subunits of bovine heart cytochrome oxidase. 20 Dec 92

Magnetic circular dichroism (MCD), electron paramagnetic resonance (EPR), and optical absorption spectroscopies have been used to monitor the concentrations of oxidized and reduced heme and copper during stoichiometric reductive titrations of purified beef heart cytochrome oxidase. The MCD data are deconvoluted to obtain the concentrations of reduced cytochromes a and a3 during the titrations; analysis of the EPR spectra provides complementary data on the concentrations of the EPR-detectable species. For the native enzyme in the absence of exogenous ligands, cytochromes a and a3 are reduced to approximately the same extent at all points in the titration. The reduction of the EPR-detectable copper, on the other hand, initially lags the reduction of the two cytochromes but in the final stages of the titration is completely reduced prior to either cytochrome a or a3. These non-Nernstian titration results are interpreted to indicate that the primary mode of heme-heme interaction in cytochrome oxidase involves shifts in oxidation-reduction potential for each of the two cytochromes such that a change in oxidation state for one of the hemes lowers the oxidation-reduction potential of the second heme by approximately 135 mV. In these titrations high spin species are detected which account for 0.25 spin/oxidase maximally. Evidence is presented to indicate that at least some of these signals can be attributed to cytochrome a3+ which has undergone a low-spin to high-spin state transition in the course of the titration. In the presence of carbon monoxide the oxidation-reduction properties of cytochromes a and a3 are markedly altered. The a32+. CO complex is fully formed prior to reduction of either cytochrome a3+ or the EPR-detectable copper. The g = 3 EPR signal attributed to cytochrome a3+ decreases as the MCD intensity of cytochrome a2+ increases; no significant high-spin intensity is observed at any intermediate stage of reduction. We interpret these Nernstian titration results to indicate that in the presence of ligands the oxidation-reduction potential of cytochrome a relative to cytochrome a3 is determined by the oxidation-reduction state of the stabilized cytochrome a3 ligand complex; if ligand binding occurs to reduced cytochrome a3 then cytochrome a titrates with a lower potential; cytochrome a titrates with a higher potential if oxidized cytochrome a3 is stabilized by ligand binding.
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PMID:The electronic state of heme in cytochrome oxidase II. Oxidation-reduction potential interactions and heme iron spin state behavior observed in reductive titrations. 20 49

The cytochrome oxidase activity of circulating leucocytes was investigated by means of a semiquantitative method using blood films. A significant decrease in activity was found in male rats, cattle and sheep that had been deprived of copper. During copper depletion, leucocyte cytochrome oxidase activity declined more slowly than did plasma copper concentration and plasma ferroxidase I activity, and so was less sensitive as a guide to the copper status of the animal.
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PMID:Changes in leucocyte cytochrome oxidase activity associated with deficiency of copper in laboratory and farm animals. 20 32

Based on the hypothesis that cross-linked elastin is critical for normal lung structure, lung tissue from copper-deficient rats was studied. Copper deficiency was induced in the second generation by feeding dams a milk-based diet low in copper (less than 1 ppm) during gestation and lactation. The weanlings were fed the same diet until they showed severe signs of deficiency between 6 and 10 weeks of age. Controls animals received the basal diet supplemented with 10 ppm copper. Liver cytochrome oxidase activity, which served as the chief index of deficiency, decreased from a normal level of approximately 80 to 15 mumole/min/g. The lungs of the deficient animals contained 17% less elastin and had 35% larger alveolar spaces (34.7 vs 47.7 intercepts), as determined by the mean alveolar intercept method. The ultrastructure of elastin in the bronchi, arterioles, and alveolar ducts had a "washed out" appearance. To determine the reversibility of the pathology, deficient animals, 5 to 10 weeks of age, were repleted by feeding a copper-supplemented diet for 1, 2, and 3 months. During this period growth resumed, anemia disappeared, and liver cytochrome oxidase returned to normal. There was no improvement in lung structure with regard to alveolar size (28.4 intercepts compared with 43.6 in controls and 35.1 in deficient littermates killed at the start of repletion). The ultrastructure and electron density of pulmonary elastin was restored to near normal. The lung of the copper-deficient rat is proposed as a model for developmental pulmonary emphysema.
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PMID:The lung of the copper-deficient rat. A model for developmental pulmonary emphysema. 20 87

Effect of cuprizone has been studied on some biochemical properties of megamitochondria obtained from the mouse liver. (1) Contents of Ca2+, Mg2+ and Cu2+ in the blood or the liver homogenates were not altered by cuprizone intoxication, whereas those in liver mitochondria were significantly altered: after 3-4 days' intoxication, content of Ca2+ was decreased and was remarkably increased after 14-15 days' intoxication. Content of Mg2+ behaved contrarily. (2) Both cytochrome oxidase and ATPase activities were unchanged in the liver megamitochondria, but monoamine oxidase (MAO) activity was significantly decreased. Value of I50 (50% inhibition) for MAO was determined to be 0.33 mM using the control liver mitochondria. Cuprizone had almost no effect on MAO activity of kidney or heart mitochondria both in vivo and in vitro. (3) The amount of lysolecithin was increased in the liver megamitochondria. These results were discussed in the light of membrane fusion phenomenon which plays a key role in the mechanism of megamitochondrial formation.
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PMID:Mechanism of the formation of megamitochondria by copper-chelating agents. V. Further studies on isolated megamitochondria. 20 65

The unique of CO-cytochrome oxidase as first noted by Yonetani et al. (22) is that after its photodissociation at low temperatures recombination occurs as the sample temperature is raised, but at temperatures considerably higher than those for other CO-heme and CO-hemoprotein complexes; that is, the half recombination temperature is 180 K contrary to 25-30 K for other CO complexes. The photodissociability, however, disappeared when monomeric cytochrome oxidase was treated with pCMB to remove an intrinsic copper, the significance of which in CO complex formation was thus demonstrated. It is proposed that the copper is situated close to heme a and traps the photodissociated CO. The access of the trapped CO to the heme a to resume the original binding is effected only when sufficient energy for thermal agitation is provided by elevating the sample temperature. During the course of this study, new photo- and thermochromic properties were observed with the reduced enzyme by cooling it in liquid nitrogen after preincubation at pH 8.6 to 10.5. The characteristic bands appeared at 575 and 428 nm and diminished when this ample was illuminated at 26 K. As the sample temperature was raised these bands were restored with a half transition temperature of 80 K. When the reduced oxidase had been complexed with CO, cyanide or azide, or treated with pCMB, such a unique species did not appear. The enthalpy change of 1.16 kcal/mol for the formation of this species as well as the above-described properties suggests that the hydrogen bond between the formyl side group of heme a and one of seven sulfhydryl groups in cytochrome oxidase is responsible for the appearance and disappearance of this new species. Based on these results a schematic model has been proposed for the photo- and thermochromism of cytochrome oxidase at cryogenic temperatures and for the microenvironment of the prosthetic heme a and copper in this enzyme. On the other hand, contrary to the central dogma of Warburg that all CO-heme and CO-hemoprotein complexes are photodissociable, we observed little photodissociability with some CO-heme complexes, especially at very low temperatures, and presented a view that depending on the bond type between CO and heme iron the efficiency of photodissociation is so varied that under certain conditions practically no photodissociation occurs. According to this view a tilted arrangement of the ligated CO towards the heme plane accompanying a large extent of overlapping of the dpi(Fe) and the pi* antibonding orbital on the CO facilitates photodissociation. In addition to our own observations of photochemical properties of cytochrome oxidase and heme model compounds, recent photodynamic studies carried out by other investigator on CO-heme and CO-hemoproteins are summarized and the validity and limitation of their models are discussed.
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PMID:Photochemical reactions of cytochrome oxidase at low temperatures. 20 71

It was found that cytochrome oxidase from bovine cardiac muscle possesses marked superoxide dismutase activity. Superoxide dismutase activity is inhibited by cyanide and azide or by alkaline or thermal treatments. This activity is also suppressed by chelating agents, e.g. bathocuproin. The data obtained indicate that superoxide dismutase activity of cytochrome oxidase is due to the copper atoms of the enzyme. The experiments on the copper-containing subunit support this conclusion. Possible physiological significance of superoxide dismutase activity of cytochrome oxidase is discussed.
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PMID:[The role of copper atoms in the cytochrome oxidase reaction]. 21 26

The temperature dependence of the paramagnetic susceptibility of cytochrome oxidase and some of its derivatives has been measured from 7 to 200 K. The results obtained for the fully oxidized (resting) enzyme correspond exactly to the requirements of the model recently proposed by Palmer et al. (Palmer, G., Babcock, G. T., and Vickery, L. E. (1976) Proc. Natl. Acad. Sci. U. S. A. 73, 2206-2210) in which the enzyme possesses two magnetically isolated spin S = 1/2 centers and a spin-coupled S = 2 center. The S = 2 center paramagnetism has been interpreted as arising from a [cytochrome a33+(S = 5/2)--Cuu2+(S = 1/2)] antiferromagnetically coupled iron.copper binuclear complex of total spin S = 2 with -J greater than or equal to 200 cm-1. In addition, the wide temperature range used in the present studies has permitted an analysis of present and other available data (T less than 4K measurements) which readily accommodates results from this and other laboratories (Moss, T.H., Shapiro, E., King, T.E., Beinert, H., and Hartzell, C. R. (1978) J. Biol. Chem 253, 8072-8073) so that a fully consistent picture of the magnetic centers in cytochrome oxidase now appears to be available. Furthermore, anomalous magnetic behavior for the oxidized enzyme.cyanide complex has been interpreted in terms of an antiferromagnetic exchange interaction operating in the binuclear complex [cytochrome a33+.CN-(S = 1/2)--Cuu2+(S = 1/2)] with -J congruent to 40 cm-1. A structural model for the [cytochrome a3(3+)-bridge-CUu2+] center is advanced in which an imidazolate ion serves as the bridging ligand in a manner similar to that found in superoxide dismutase.
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PMID:Electronic state of heme in cytochrome oxidase III. The magnetic susceptibility of beef heart cytochrome oxidase and some of its derivatives from 7-200 K. Direct evidence for an antiferromagnetically coupled Fe (III)/Cu (II) pair. 21 27


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