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)

The resonance Raman spectra of deoxygenated solutions of mixed-valence cyanide-bound and fully reduced cytochrome oxidase derivatives that have been reduced in the presence of aqueous or solid sodium dithionite exhibit two new low-frequency lines centered at 474 and 590 cm-1. These lines were not observed when the reductant system was changed to a solution containing ascorbate and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD). Under enzyme turnover conditions, the addition of dithionite to the reoxidized protein (the 428-nm or "oxygenated" form) increases the intensity of these lines, while reoxidation and rereduction of the enzyme in the presence of ascorbate/TMPD resulted in the absence of both lines. Our data suggest that both lines must have contributions from species formed from aqueous dithionite, presumably the SO2 species, since these two lines are also observed in the Raman spectrum of a solution of aqueous dithionite, but not in the spectrum of an ascorbate/TMPD solution. Since heme metal-ligand stretch vibrations are expected to appear in the low-frequency region from 215 to 670 cm-1, our results indicate that special care should be exercised during the interpretation of the cytochrome a3 resonance Raman spectrum.
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PMID:Evidence of dithionite contribution to the low-frequency resonance Raman spectrum of reduced and mixed-valence cytochrome c oxidase. 130 79

Anaerobic reduction of cytochrome c oxidase by 5,10-dihydro-5-methylphenazine (reduced PMS) and by sodium dithionite were studied by rapid scanning stopped flow spectrophotometry. In both cases the decay of the Soret band of the oxidized oxidase is not uniform. With reduced PMS, the reduction involves two molecules of reductant (4 electrons)/oxidase molecule. The first stage of the reduction exhibits an isosbestic point in the Soret region at 437 nm. This shifts to 428 nm in later stages of the reaction. The reduction of the oxidase by sodium dithionite is also complete and apparently involves SO2 radical. In this case the spectra show an isosbestic point at approximately 420 nm which shifts to 432 nm as the reaction proceeds. For each of the reductants the reaction is best described by three phases: the first is a second order reaction between the oxidase and the reductant, followed by two first order processes which appear to describe the intramolecular electron redistribution within the oxidase molecule. The results agree with the assignment of the Soret band of the oxidase molecule to cytochrome a3 with an absorption maximum near 410 nm and to cytochrome a which has its maximum absorption hear 430 nm. If these assignments are correct, the present data show that reduced PMS, an uncharged molecule, reacts more rapidly with cytochrome a than it does with cytochrome a3, while the negatively charged radical anion, SO2, appears to have more direct access to cytochrome a3.
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PMID:Kinetic distinction between cytochromes a and a3 in cytochrome c oxidase. Rapid scanning stopped flow study of anaerobic reduction by a neutral and a negatively charged donor. 625 79

The reduction of cytochrome c oxidase (EC 1.9.3.1) by dithionite was investigated by stopped-flow spectrophotometry and flow-flash techniques in the presence of CO. Of the two haem groups present in the enzyme, that associated with cytochrome alpha is the first reduced. The second-order rate constants for reduction of a number of redox proteins (cytochrome c, stellacyanin and azurin) by the S2O4(2-) and SO2.- anions are reported, and the values are compared with those determined for cytochrome c oxidase. These results are discussed in terms of the accessibility and charge distribution of the electron-entry site of cytochrome c oxidase.
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PMID:Reactions of cytochrome c oxidase with sodium dithionite. 630 99

Changes in the hepatic oxygenation state of rabbits during hemorrhage and subsequent epinephrine (n = 6) or dextran infusion (n = 6) were assessed by tissue near-infrared spectroscopy. Oxygen saturation of hemoglobin in the liver (hepatic SO2), and redox transition of cytochrome aa3 were analyzed by applying multicomponent analysis to the absorption spectrum of the liver. Hepatic SO2, representing extracellular oxygenation state, decreased from 62.4 +/- 2.7% (mean +/- SEM) to 21.1 +/- 7.3% after bleeding. It increased to 31.8 +/- 6.6% after epinephrine infusion, but returned to near-control levels after dextran infusion. Intracellular oxygenation state as assessed by the changes in the oxidized and reduced forms of cytochrome aa3 was impaired after bleeding, and remained as such even after epinephrine infusion. By contrast, it was normalized to near control levels after dextran infusion. Changes in the difference of hepatic SO2 and hepatic venous SO2 suggested that the intrahepatic blood flow was more heterogeneously distributed after bleeding, but that the heterogeneity of microcirculation was rather diminished after epinephrine infusion.
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PMID:Changes in the hepatic oxygenation state during hemorrhage and following epinephrine or dextran infusion as assessed by near-infrared spectroscopy. 750 28

The rapid changes in extracellular oxygenation and intracellular oxidation during ischemia and reflow were measured in deep liver tissue by a novel method combining tissue near-infrared spectroscopy with multicomponent curve-fitting analysis. This method enabled us to make real-time measurements of oxygen saturation (SO2) and amount (THB) of hemoglobin in the liver sinusoid as parameters of extracellular oxygenation state and of redox transition of cytochrome aa3 as intracellular oxidation state. Clamping of the hepatic artery in rabbit decreased the THB with a transient fall of SO2. Clamping of the portal vein decreased both SO2 and THB. The decreases of SO2 and THB caused by Pringle's maneuver were larger than the sum of decreases by hepatic artery and portal vein. These changes in SO2 were correlated with intramitochondrial oxidation state as measured by cytochrome aa3. These results indicate the presence of an interrelationship of oxygen supply by hepatic artery and portal vein. This method was clinically applied during and after clamping of hepatic artery and portal vein in 19 cases of hepatic resection with or without chronic hepatic diseases. The decrease in SO2 values before and after clamping (SO2D) and the slope of SO2 recovery (SO2R) after release were calculated. SO2D and SO2R values of the portal vein in cirrhotics were significantly higher and lower, respectively, than those in the normal liver. These data indicate that the present method provides a rapid and reliable method of quantifying hepatic oxygenation during liver surgery and its perioperative management.
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PMID:Interrelationship of oxygen supply by hepatic artery and portal vein: rapid analysis of ischemia-reflow-induced changes in hepatic oxygenation in experimental and clinical subjects by tissue near-infrared spectroscopy. 785 60

A microscopic reflectance spectrophotometer was constructed to obtain the spectra of single pial vessels and of a region containing only capillaries (capillary region). The difference in the oxygen saturation (SO2) of hemoglobin between the regional arteriole and venule [R(A - V)] and that between the regional arteriole or capillaries [R(A - C)] were calculated. The reduction of cytochrome aa3 was also estimated in the capillary region. This method was applied to the brain surface of spontaneously breathing rats subjected to hypoxic and anemic hypoxia. On decreasing the inhaled O2 from 100 to 15%, elevation of R(A - V) and R(A - C) with slight arteriolar dilatation (though statistically not significant) was observed. Below 10% O2 (especially at 4 and 3% O2), the R(A - V) and R(A - C) decreased in spite of significant arteriolar dilatation with progressive reduction of cytochrome aa3, indicating suppression of oxygen transport to mitochondria. In the case of hemodilution down to 37% hematocrit (Ht), elevation of R(A - V) and R(A - C) occurred with a slight tendency toward arteriolar dilatation. Below 32% Ht, the R(A - V) decreased but the R(A - C) remained steady, while reduction of cytochrome aa3 progressed. Altogether, the SO2 in the capillary region decreased and the reduction of cytochrome aa3 progressed with the decline of arteriolar O2 supply in both hypoxic and anemic hypoxia.
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PMID:Intravital microreflectometry of individual pial vessels and capillary region of rat. 826 61

We report the use of steady-state diffuse reflectance spectroscopy (SSDRS) to measure the near-infrared absorption spectrum of liquid phantoms containing human erythrocytes in aqueous suspensions of polystyrene spheres which simulate the scattering properties of tissue. The absorption spectra obtained from these SSDRS measurements of intact red cells under oxygenated and deoxygenated conditions are compared with several published spectra of 'stripped' haemoglobin prepared from lysed cells. Two fitting algorithms (nonlinear least squares and singular value decomposition) which exploit the broad spectral range provided by these measurements (170 data points spanning 164 nm in a single acquisition) are used to determine haemoglobin oxygen saturation (SO2) from SSDR spectra collected over a wide range of measured oxygen partial pressures. The validity of these algorithms is assessed by comparing literature values of p50 (the oxygen tension at which haemoglobin is 50% saturated) and the Hill coefficient to values of these parameters determined from the SO2 estimates. The singular value decomposition algorithm can also be used to reconstruct the non-haemoglobin background absorption spectrum without a priori assumptions regarding its constituent chromophores or their concentrations. Using this technique, the absorption spectrum of a small amount of India ink (maximum absorption coefficient (mu(a max)) approximately 0.0006 mm(-1)) added to a phantom containing red cells (mu(a max) approximately 0.026 mm(-1)) was reconstructed over a full range of oxygen saturations. The implications of these measurements for detection of weakly absorbing chromophores (such as cytochrome aa3) in the presence of haemoglobin are discussed.
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PMID:Quantitative broadband near-infrared spectroscopy of tissue-simulating phantoms containing erythrocytes. 983 22

Reflection near infrared spectroscopy (reNIRS) has been proposed as a novel technique for the measurement of absolute values of total hemoglobin (tHb), oxygenated hemoglobin (oxHb), hemoglobin saturation (SO2), and cytochrome aa3 oxidation status (oxCyt aa3) in living tissue. In this study, we evaluated reNIRS during physiological cerebral blood flow conditions in rats (n=6) and during the induction of global cerebral ischemia in gerbils (n=6). ReNIRS parameters were assessed over the exposed cerebral cortex and compared to regional cerebral blood flow (rCBF) data obtained by laser Doppler flowmetry. Under physiological conditions, reNIRS measurements reflected the large intra- and interindividual variability of oxHb and tHb in the brain. The absolute values obtained by reNIRS for tHb (6.3 +/- 1.7 mg/ml), oxHb (3.7 +/- 1.1 mg/ml), and SO2 (61 +/- 5%) matched expected values. In contrast, measurements of oxCyt aa3 were unstable and results unreliable. reNIRS reliably detected cerebral ischemia, verified by a reduction of rCBF to 11% of baseline. tHb dropped to 74 +/- 7% of baseline (P<0.001), reflecting ischemic microvascular vasoconstriction. oxHb and SO2 dropped to expected near-zero values (2 +/- 4 and 3 +/- 5% of baseline, respectively; P<0.001). We conclude that reNIRS provides reliable and reproducible absolute values for brain tissue tHb, oxHb, and SO2 in small rodents. Determination of physiological values requires measurements at multiple locations, while cerebral ischemia is reliably detected by continuous recordings at a single location.
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PMID:Measurement of absolute values of hemoglobin oxygenation in the brain of small rodents by near infrared reflection spectrophotometry. 1185 62