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)

A microsomal fraction, prepared from mouse skin, catalyzed the hydroxylation of benzpyrene and aniline and the deethylation of 7-ethoxycoumarin. Contamination of the preparation by cytochrome oxidase and cytochrome P-420 was determined by spectral analysis. The enzyme activities studied in mouse skin (Swiss-Webster CD-1) did not respond to topical application of 3-MC. Twenty-four hours after topical application of TCDD to mice, microsomes from skin had 50% greater benzpyrene hydroxylase and 7-ethoxycoumarin deethylase activity, and 4- to 8-fold greater activity of these enzymes was seen after 72 hr. Increases in cytochrome P-450 content of skin microsomes could be demonstrated 24 and 72 hr after topical TCDD treatment of mice. Cholate treatment (solubilization) of skin microsomes, followed by centrifugation, removed the contaminating cytochrome oxidase. Quantitative and qualitative analyses of cytochrome P-450 difference spectra were made from the solubilized preparations.
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PMID:Cytochrome P-450 content and mixed-function oxidase activity in microsomes isolated from mouse skin. 1 Jan 43

Flash photolysis has been used to effect electron transfer from tris(2,2'-bipyridyl)ruthenium(II) to cytochrome c oxidase in the presence of a sacrificial electron donor, aniline. The observation that photoreduction occurs only at low ionic strength and high pH indicates that an electrostatic complex between the ruthenium compound and the enzyme is the reactive species. The reaction was followed at 830, 605, and 445 nm. The initial absorbance changes observed suggest that the copper ion CuA is the preferred electron acceptor and that electron transfer from the excited ruthenium complex takes place in less than 1 microsecond. Some rapid cytochrome a reduction is also observed. Absorbance changes after the initial transients suggest that the reduced CuA then equilibrates with cytochrome a with a rate constant of 2 x 10(4) s-1. Comparison of the absorbance changes at 605 and 445 nm and the kinetic difference spectrum in the Soret region indicate that no reduction of cytochrome a3 takes place. With the oxidized enzyme, no further reactions were detected, whereas, in the peroxide and ferryl intermediates, cytochrome a reoxidizes on a millisecond time scale. The reaction appears biphasic in both intermediates, with rate constants in the range 2 x 10(2) to 4 x 10(3) s-1. This is considerably slower than the maximal rates observed for electron transfer between cytochrome a and the bimetallic site found in earlier work and suggests rate limitation by other processes. The rates obtained for the slower phases are close to the rate for catalysis of cytochrome c oxidation.
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PMID:Photoinduced electron transfer from tris(2,2'-bipyridyl)ruthenium to cytochrome c oxidase. 132 42

Fascioliasis has been produced in the rat by an oral administration of 20 metacercariae of Fasciola hepatica. Hepatic microsomal cytochrome P450 and b5 contents and both aminopyrine demethylase and aniline hydroxylase activities have been measured during the course of the experimental distomiasis. The cytochrome P450 concentration and microsomal drug metabolizing enzymes generally fell by weeks 3 to 8 post-infestation and recovered to normal values thereafter. For the same period, both the histoenzymatically assayed liver cytochrome oxidase and arylsulphatase activities were reduced whereas there were correlated increases in glutamic pyruvic and glutamic oxaloacetic plasma transaminases. Tissue inflammation and destruction provoked by young histophagous migrating flukes could be responsible for these changes that have already been observed in several hepatic diseases. The possible influence of naturally-induced fasciolasis on liver drug metabolism is discussed.
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PMID:Impairment of drug metabolism by the liver in experimental fascioliasis in the rat. 613 54

Monkeys (Macaca nemestrina) were divided into four groups, and each group was fed a particular diet. The variables in the diets were as follows: diet A, 0.3 mg cholesterol/kcal nutrient; diet B, 1.0 mg cholesterol/kcal nutrient; diet C, 0.3 mg cholesterol/kcal nutrient, ethanol (36% of calories); diet D, 1.0 mg cholesterol/kcal nutrient, ethanol (36% of calories). Monkeys on the diets containing ethanol developed fatty liver. Mitochondria from ethanol-fed animals demonstrated significant decreases in uncoupler-stimulated, state 3, and state 4 succinate oxidation activity; respiratory control ratio; and ATP content. Liver microsomes isolated from the ethanol-fed groups demonstrated increased ethanol oxidizing activity with either NADPH or H2O2 as cosubstrate. Aniline hydroxylase and aminopyrine-N-demethylase activities were also elevated in ethanol-fed animals. The alterations in these functional properties were related primarily to ethanol in the diets. Cholesterol, while being less of a perturbant than ethanol, did elicit a significant decrease in cytochrome oxidase activity of mitochondria and a small but statistically significant increase in microsomal-associated ethanol oxidation activity. It appeared to potentiate the effect of ethanol in lowering mitochondrial respiratory control and ATP concentrations.
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PMID:Effect of dietary ethanol and cholesterol on metabolic functions of hepatic mitochondria and microsomes from the monkey, Macaca nemestrina. 702 93

The first step in the catalytic cycle of cytochrome oxidase, the one-electron reduction of the fully oxidized enzyme, was investigated using a new photoactive binuclear ruthenium complex, [Ru(bipyrazine)2]2(quaterpyridine), (Ru2Z). The aim of the work was to examine differences in the redox kinetics resulting from pulsing the oxidase (i.e., fully reducing the enzyme followed by reoxidation) just prior to photoreduction. Recent reports indicate transient changes in the redox behavior of the metal centers upon pulsing. The new photoreductant has a large quantum yield, allowing the kinetics data to be acquired in a single flash. The net charge of +4 on Ru2Z allows it to bind electrostatically near CuA in subunit II of cytochrome oxidase. The photoexcited state Ru(II*) of Ru2Z is reduced to Ru(I) by the sacrificial electron donor aniline, and Ru(I) then reduces CuA with yields up to 60%. A stopped-flow-flash technique was used to form the pulsed state of cytochrome oxidase (the "OH" state) from several sources (bovine heart mitochondria, Rhodobacter sphaeroides, and Paracoccus denitrificans). Upon mixing the fully reduced anaerobic enzyme with oxygenated buffer containing Ru2Z, the oxidized OH state was formed within 5 ms. Ru2Z was then excited with a laser flash to inject one electron into CuA. Electron transfer from CuA --> heme a --> heme a3/CuB was monitored by optical spectroscopy, and the results were compared with the enzyme that had not been pulsed to the OH state. Pulsing had a significant effect in the case of the bovine oxidase, but this was not observed with the bacterial oxidases. Electron transfer from CuA to heme a occurred with a rate constant of 20,000 s-1 with the bovine cytochrome oxidase, regardless of whether the enzyme had been pulsed. However, electron transfer from heme a to the heme a3/CuB center in the pulsed form was 63% complete and occurred with biphasic kinetics with rate constants of 750 s-1 and 110 s-1 and relative amplitudes of 25% and 75%. In contrast, one-electron injection into the nonpulsed O form of the bovine oxidase was only 30% complete and occurred with monophasic kinetics with a rate constant of 90 s-1. This is the first indication of a difference between the fast form of the bovine oxidase and the pulsed OH form. No reduction of heme a3 is observed, indicating that CuB is the initial electron acceptor in the one-electron reduced pulsed bovine oxidase.
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PMID:A new ruthenium complex to study single-electron reduction of the pulsed O(H) state of detergent-solubilized cytochrome oxidase. 1802 81