Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Specific activities of succinate:coenzyme Q reductase, ubiquinone:cytochrome c reductase, cytochrome oxidase, succinate:cytochrome c reductase, succinate oxidase, and ubiquinol oxidase have been measured in rat liver mitochondria in the presence of Triton X-100. The last three activities are much more sensitive to Triton X-100 than the first ones; the data suggest that the electron transport chain components cannot react with each other in the presence of the detergent. At least in the case of succinate:cytochrome c reductase, reconstitution of the detergent-treated membranes with externally added phospholipids reverses the inhibition produced by Triton X-100. These results support the idea that the respiratory chain components diffuse at random in the plane of the inner mitochondrial membrane; the main effect of the detergent would be to impair lateral diffusion by decreasing the area of lipid bilayer. When detergent-treated mitochondrial suspensions are centrifuged in order to separate the solubilized from the particulate material, only the first three enzyme activities mentioned above are found in the supernatants. After centrifugation, a latent ubiquinol:cytochrome c oxidase activity becomes apparent, whereas the same centrifugation process produces inhibition of cytochrome c oxidase in the presence of certain Triton X-100 concentrations. These effects could be due either to a selective solubilization of regulatory or catalytic subunits or to a conformational change of the enzyme-detergent complex.
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PMID:Effect of the nonionic detergent Triton X-100 on mitochondrial succinate-oxidizing enzymes. 632 Jul 42

It has been shown that in bovine heart submitochondrial particles, antimycin and 2-heptyl-4-hydroxyquinoline N-oxide (HQNO) inhibit the oxidation of NADH, succinate, and reduced ubiquinone incompletely, the uninhibited rate being about 20-40 nmol of substrate oxidized min-1 (mg of protein)-1. By contrast, rotenone, cyanide, BAL (2,3-dimercaptopropanol), and 5-n-undecyl-6-hydroxy-4,7-dioxobenzothiazole [Trumpower, B. L., & Haggerty, J. G. (1980) J. Bioenerg. Biomembr. 12, 151-164] caused essentially complete inhibition when added alone or after maximal inhibition by antimycin or HQNO. Having thus ascertained that the electron leak through the antimycin block appeared to follow the normal path through complex III (ubiquinol: cytochrome c oxidoreductase) and cytochrome oxidase, the reduction of the b cytochromes by substrates and their oxidation through the leak in the antimycin block by molecular oxygen were studied. It was shown that at normal electron flux from NADH and succinate, both cytochromes b562 and b566 were reduced in antimycin-treated submitochondrial particles. Their oxidation after substrate exhaustion was biphasic, however. At 565 minus 575 nm, 56% of the total reduced cytochrome b was oxidized through the leak in the antimycin block at a more rapid rate, while the remaining 44% was oxidized about 10 times slower. When electron flux from substrates to complex III was slowed down by the use of inhibitors or substrates at less than or equal to 0.1 Km concentration, then only reduced b562 accumulated in antimycin-treated particles. The oxidation of b562 after substrate exhaustion or inhibition of substrate oxidation by an appropriate inhibitor occurred at a rate comparable to that of the slower reoxidation phase described above. These results indicated, therefore, that cytochromes b566 and b562 are oxidized through the leak in the antimycin block at two different rates, the reoxidation rate of b566 being about 10 times faster than that of b562. The implications of these findings on the kinetic relationship of these two cytochromes in the respiratory chain have been discussed.
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PMID:Kinetics of cytochrome b oxidation in antimycin-treated submitochondrial particles. 715 May 80

The impairment of the complexes of the respiratory chain was studied in isolated rat liver mitochondria under the conditions of an iron/ascorbate-mediated oxidative stress. Using blue native electrophoresis technique the NADH-ubiquinone oxidoreductase, ubiquinol-cytochrome-c oxidoreductase, cytochrome oxidase and ATP-synthetase were separated from mitochondrial samples at different stages of peroxidation and quantified by densitometry. In the second dimension the protein complexes were separated into their individual subunits by Tricine/SDS-electrophoresis. In relation to the time course of lipid peroxidation protein losses were moderate in the exponential phase and enhanced towards plateau phase of TBARS formation, when the intensity of staining for the native complexes became reduced by 84%, 69%, 63% and 24% for complexes I, III, V and IV, respectively, and a high molecular aggregation band as a putative marker of oxidative stress was formed. The decline of overall staining by 23%, a decrease in trichloroacetic acid precipitable protein and the formation of acid soluble primary amines suggest the occurrence of fragmentation or degradation processes. Apparently, the impairment of the respiratory chain complexes during peroxidation was not reflected in altered electrophoretic mobilities or specific losses of protein subunits of these innermitochondrial membrane components.
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PMID:Electrophoretic evidence for the impairment of complexes of the respiratory chain during iron/ascorbate induced peroxidation in isolated rat liver mitochondria. 754 43

We have investigated the respiratory activities and the concentrations of respiratory chain components of mitochondria isolated from the livers and hearts of two groups of rats aged 6 and 24 months respectively. In comparison with the adult controls (6 months), in aged rats there was a decline in total aerobic NADH oxidation in both tissues; only minor (non-significant) changes, however, were found in NADH:coenzyme Q reductase and cytochrome oxidase activities, and there was no change in ubiquinol-cytochrome c reductase activity. The coenzyme Q levels were slightly decreased in mitochondria from both organs of aged rats. The lowered NADH oxidase activity is not due to the slight decrease observed in the coenzyme Q levels, but is the result of decreased Complex I activity. Since the assay of NADH:coenzyme Q reductase requires quinone analogues, none of which can evoke its maximal turnover [Estornell, Fato, Pallotti and Lenaz (1993) FEBS Lett. 332, 127-131], its activity has been calculated indirectly by taking advantage of the relationship that exists between NADH oxidation and ubiquinol oxidation through the coenzyme Q pool. The results, expressed in this way, show a drastic loss of activity of Complex I in both the heart and the liver of aged animals in comparison with adult controls.
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PMID:Major changes in complex I activity in mitochondria from aged rats may not be detected by direct assay of NADH:coenzyme Q reductase. 757 40

A screen has been performed of possible inhibitors of the ubiquinol oxidase of higher plant mitochondria by assaying their effects on cyanide-insensitive NADH oxidase of mitochondria of Arum maculatum. A number of compounds which have powerful inhibitory effects have been identified. Potent inhibition was found with compounds related to the previously described n-propyl gallate, but with the n-propyl sidechain replaced with alkyl chains of greater hydrophobicity. Titration of a range of partial reactions showed that the inhibitors act specifically on the ubiquinol oxidase. The concentrations of inhibitor required are dependent on the respiratory substrate and on the amount of mitochondria used in the assay. Octyl gallate also proved to be a potent inhibitor of the ubiquinol oxidase in tobacco cell suspensions. A second class of compounds which strongly inhibit cyanide-insensitive NADH oxidation is aurachin C and its analogues. Compounds related to aurachin D are much less effective. Titrations of a range of partial reactions indicate that inhibition is caused by a direct action on the ubiquinol oxidase. However, both types of aurachins also act strongly at the Qi site of the cytochrome bc1 complex, as already known to be the case in other systems, and so they are of more limited value for studies of the ubiquinol oxidase. Titration of the oxidation of NADH via the ubiquinol oxidase in a purified mitochondrial fraction from the spadices of Arum maculatum with octyl gallate gave a half-maximal effect at a concentration of around 6 nM when the protein concentration was 14 micrograms ml-1. A similar titre was obtained with a decyl derivative of aurachin C. This allowed us to estimate an upper limit for the concentration of ubiquinol oxidase in these mitochondria of 0.72 +/- 0.15 nmol mg-1 protein, or a ratio of ubiquinol oxidase/cytochrome oxidase of about 15 +/- 7:1. The measurements also provide a minimal turnover number for the ubiquinol oxidase of 186 +/- 42 electrons.s-1. Titration of the ubiquinol oxidase in soybean cotyledon mitochondria with these compounds gave the concentration of inhibitor required to elicit 50% of the maximum observed effect (I50) values about one order of magnitude higher than those found with Arum mitochondria, and again the values depended on the respiratory substrate. An explanation for the variation in I50 values may be found in terms of differences in oxidase concentrations in the different mitochondrial membranes and in the differences in rate-controlling steps with substrates of different activities.
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PMID:New inhibitors of the ubiquinol oxidase of higher plant mitochondria. 758 98

The RCA1 (YTA12) and AFG3 (YTA10) genes of Saccharomyces cerevisiae code for homologous mitochondrial proteins that belong to the recently described AAA protein-family [Kunau et al. (1993) Biochimie 75,209-224]. Mutations in either gene have been shown to induce a respiratory defect. In the case of rca1 mutants this phenotype has been ascribed to defective assembly of cytochrome oxidase and ubiquinol-cytochrome c reductase. In the present study we show that the respiratory defect of afg3 mutants, like that of rca1 mutants, is also caused by an arrest in assembly of cytochrome oxidase and ubiquinol-cytochrome c reductase. In addition to the absence of the respiratory complexes, rca1 and afg3 mutants exhibit reduced mitochondrial ATPase activity. As a first step to an understanding of the biochemical basis for the ATPase defect we have examined the assembly of the F1 and F0 constituents of the ATPase complex. We present evidence that the ATPase lesion stems at least in part from the failure of rca1 and afg3 mutants to assemble F1. Although the mutants also display lower steady-state concentrations of some F0 subunits, this could be a secondary effect of defective F1 assembly.
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PMID:Mutations in RCA1 and AFG3 inhibit F1-ATPase assembly in Saccharomyces cerevisiae. 758 36

F1F0 ATP-synthase (complex V) deficiencies in Alzheimer's disease are reported. Tissue specimens from the hippocampus of brains from patients with Alzheimer's disease were screened by blue native electrophoresis for alterations of the proteins of oxidative phosphorylation. Ubiquinol:cytochrome-c reductase (complex III) and cytochrome-c oxidase (complex IV) were found to be present at almost normal concentrations, however, complex V was substantially reduced in most cases studied. The specific reduction of complex V and the absence of electrophoretically detectable degradation products do not exclude a secondary defect of complex V, but should stimulate the search for genetic defects related to protein subunits of complex V.
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PMID:Human diseases with defects in oxidative phosphorylation. 2. F1F0 ATP-synthase defects in Alzheimer disease revealed by blue native polyacrylamide gel electrophoresis. 786 55

Some analytical and functional parameters of rat heart mitochondrial have been investigated at six different periods of ageing from 2 to 26 months. The fatty acid composition of the mitochondrial membranes reveals a percentage increase of polyunsaturated fatty acids (20:4 n-6, 22:6 n-3) up to 12 months, followed by a decrease; however, fluorescence polarization of the membrane probe diphenylhexatriene is not changed, revealing that membrane fluidity is not significantly affected. No major change in ubiquinone-9 and in cytochrome content is apparent, indicating that the relative ratio of the respiratory chain components is unmodified. Nevertheless, significant changes in enzyme specific activities are detected: NADH cytochrome c reductase and cytochrome oxidase activities increase up to 12 months, then decrease at 18-26 months; ubiquinol cytochrome c reductase exhibits a peak at 18 months, followed by a decrease. All these activities follow a similar trend during the whole life span of the rat, even though the 'maximum' is different. No significant changes have been found in ATP synthase. Succinate-cytochrome c reductase steadily increases over the whole life span. The results, showing activity decreases in the respiratory enzymes having subunits encoded by mitochondrial DNA, are compatible with the 'mitochondrial' theory of ageing.
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PMID:Mitochondrial activities of rat heart during ageing. 788 68

To evaluate the effects of physical training on mitochondrial gene expression and mitochondrial biogenesis in slow-twitch muscle, adult female Sprague-Dawley rats were trained for 3, 6, and 12 wk by running on a motor-driven treadmill (speed of 25 m/min and duration of 90 min/day, 5 days/wk), and the activities of citrate synthase, ubiquinol-cytochrome-c oxidoreductase, cytochrome oxidase, mitochondrial cytochrome b mRNA (by Northern blot analysis), and mitochondrial DNA (by slot-blot and Southern blot analyses) were measured in rat soleus muscle. A DNA probe for detection of mitochondrial mRNA and DNA was prepared from a 1,500-bp fragment of human mitochondrial DNA that included the coding region of the cytochrome b gene. Training for 3, 6, and 12 wk significantly increased the activities of citrate synthase (31, 28, and 47%, respectively), ubiquinol-cytochrome-c oxidoreductase (61, 63, and 77%, respectively), and cytochrome oxidase (25, 26, and 32%, respectively) in muscle. The concentration of cytochrome b mRNA in the muscle was proportionally elevated with the enzyme activities. On the other hand, the mitochondrial DNA concentration in the muscle was not altered by training for 3 or 6 wk but increased significantly after training for 12 wk (35% in the slot-blot analysis and 31% in the Southern blot analysis). These results suggest that an increase in the oxidative capacity of slow-twitch muscle by the relatively short-term training is regulated at the pretranslational step in mitochondrial protein synthesis but that the increase by the long-term training involves mitochondrial replication.
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PMID:Enzymatic and genetic adaptation of soleus muscle mitochondria to physical training in rats. 794 19

A correlation between dietary lipids and cellular enzyme activities is a problem that has only been partially addressed by nutritionists. Therefore, changes in the fatty acid composition and the activities of some key metabolic enzymes (ubiquinol-2-cytochrome c reductase (EC 1.10.2.2), cytochrome oxidase (EC 1.9.3.1) and ATPase (EC 3.6.1.3)) in the mitochondria of liver, heart and brain of rats fed on diets differing extensively in their polyunsaturated fatty acid compositions have been investigated. The results showed that fatty acid compositional changes brought about by the dietary differences were associated with extensive changes in the activities of these key enzymes in the mitochondria. The extent of the influence differed considerably with the period over which the diets were fed. The role of dietary lipids to effect changes through the preservation of membrane structural integrity is discussed.
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PMID:The effect of dietary lipid changes on the fatty acid composition and function of liver, heart and brain mitochondria in the rat at different ages. 814 31


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