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PubMed1992

Effect of chronic respiratory load on cytochrome oxidase activity in diaphragmatic fibers.

To determine whether the increase in oxidative capacity after respiratory muscle training with chronic inspiratory loads in sheep is specific to a particular fiber type, we measured cytochrome c oxidase (COX) activity in type I and type II fibers. COX activity in individual fibers was examined histochemically and measured as relative optical density by use of an image processing system. Fiber types were differentiated by the myosin adenosine-triphosphatase reaction. We found that COX activity was higher in both fiber types in the trained diaphragms than in the control diaphragms (P less than 0.01). The increase with training was greater in type II (39%) than in type I fibers (21%), resulting in relatively homogeneous COX activity in all diaphragmatic fibers. The proportion of type I fibers increased from 43.4 +/- 5.4% in the control diaphragm to 53.1 +/- 2.9% in the trained diaphragm, whereas the proportion of type II fibers decreased (P less than 0.001). We conclude that respiratory muscle training activates oxidative enzyme activity in both diaphragmatic fiber types; this activation is differentially more in type II fibers, which also decrease in proportion, and less in type I fibers, which increase in proportion.

Airway Resistance↗
PubMed1992

Altered activity of hepatic mixed function oxidase, cytochrome P-450 and glutathione-S-transferase by styrene in rat fetal liver.

The effect of in utero exposure to styrene 200 or 400 mg/kg/day orally was studied on mixed function oxidase activities, cytochrome P-450 and glutathione contents and on the glutathione-S-transferase activity in rat fetal liver. Activities of aminopyrene-N-demethylase, aniline hydroxylase, aryl hydrocarbon hydroxylase and the cytochrome P-450 contents were significantly decreased in the fetal liver. A significant decrease in the glutathione contents and the glutathione-S-transferase activity was also observed in the liver of the fetuses of styrene exposed animals. The current data show that prenatal exposure to styrene could adversely affect the developing biotransformation process.

Animals↗
PubMedDate not supplied

Progressive cerebral degeneration of childhood with liver disease (Alpers Huttenlocher disease) with cytochrome oxidase deficiency presenting with epilepsia partialis continua as the first clinical manifestation.

A previously healthy and normally developed 17-year-old young female presented with a sudden onset of focal motor seizure status that proved to be refractory to anticonvulsive treatment. Severe encephalopathy with visual impairment leading to blindness, mental deterioration, and predominantly left spastic tetraparesis developed progressively. Hepatic disease evolved 4 months after onset of the first symptoms and led to death in hepatic failure 1 month later. Diagnostic studies revealed an elevated protein and lactate in the cerebrospinal fluid, slow-wave and intermittently continuous spike-wave activity in the EEG, and a complex i.v. (cytochrome-C oxidase) deficiency in the muscle biopsy. MRI scans revealed signal abnormalities in the occipital lobe, thalamus, and basal ganglia only after 3 months. Histopathological findings in liver biopsy and in postmortem brain examination displaying widespread predominantly right cortical spongiosis, neuronal loss and astrocytosis were consistent with the clinically suspected diagnosis of progressive neuronal degeneration of childhood with liver disease (PNDC) or Alpers Huttenlocher disease. This rare disorder of unknown origin is usually seen in infants and young children and is rarely reported in adolescence.

Adolescent↗
PubMed2003

Nitric oxide and cytochrome oxidase: reaction mechanisms from the enzyme to the cell.

The aim of this work is to review the information available on the molecular mechanisms by which the NO radical reversibly downregulates the function of cytochrome c oxidase (CcOX). The mechanisms of the reactions with NO elucidated over the past few years are described and discussed in the context of the inhibitory effects on the enzyme activity. Two alternative reaction pathways are presented whereby NO reacts with the catalytic intermediates of CcOX populated during turnover. The central idea is that at "cellular" concentrations of NO (</= microM), the redox state of the respiratory chain results in the formation of either the nitrosyl- or the nitrite-derivative of CcOX, with potentially different metabolic implications for the cell. In particular, the role played by CcOX in protecting the cell from excess NO, potentially toxic for mitochondria, is also reviewed highlighting the mechanistic differences between eukaryotes and some prokaryotes.

Animals↗
PubMed1999

Characterization of an operon encoding two c-type cytochromes, an aa(3)-type cytochrome oxidase, and rusticyanin in Thiobacillus ferrooxidans ATCC 33020.

Despite the importance of Thiobacillus ferrooxidans in bioremediation and bioleaching, little is known about the genes encoding electron transfer proteins implicated in its energetic metabolism. This paper reports the sequences of the four cox genes encoding the subunits of an aa(3)-type cytochrome c oxidase. These genes are in a locus containing four other genes: cyc2, which encodes a high-molecular-weight cytochrome c; cyc1, which encodes a c(4)-type cytochrome (c(552)); open reading frame 1, which encodes a putative periplasmic protein of unknown function; and rus, which encodes rusticyanin. The results of Northern and reverse transcription-PCR analyses indicated that these eight genes are cotranscribed. Two transcriptional start sites were identified for this operon. Upstream from each of the start sites was a sigma70-type promoter recognized in Escherichia coli. While transcription in sulfur-grown T. ferrooxidans cells was detected from the two promoters, transcription in ferrous-iron-grown T. ferrooxidans cells was detected only from the downstream promoter. The cotranscription of seven genes encoding redox proteins suggests that all these proteins are involved in the same electron transfer chain; a model taking into account the biochemistry and the genetic data is discussed.

Azurin↗
PubMed1997

The cytochrome oxidase subunit 1 gene (cox1) from the dinoflagellate, Crypthecodinium cohnii.

To date, no genes have been characterized from dinoflagellate mitochondrial DNA. Here we present the complete sequence of the gene (cox1) encoding subunit 1 of cytochrome c oxidase in the dinoflagellate, Crypthecodinium cohnii. Analysis of nucleotide and deduced amino acid sequences predicts a protein of 523 amino acids that is translated using universal initiation, stop and tryptophan codons. COX1 amino acid identity and phylogenetic tree analyses strongly support a close evolutionary relationship between dinoflagellates and apicomplexans; however, inclusion of the ciliates in this clade is less well supported, a result likely due to the highly derived nature of ciliate COX1 sequences.

Amino Acid Sequence↗
PubMed1980

Reduction of oxygen-pulsed cytochrome c oxidase by cytochrome c and other electron donors.

1. Stopped-flow experiments were performed in which solutions containing dithionite were mixed with air-saturated buffer. Cytochrome c oxidase present in the dithionite-containing syringe is fully oxidized within the mixing time and the oxygen-pulsed form of the oxidase is produced. 2. The reduction of this form by dithionite, by dithionite plus cytochrome c and by dithionite plus methyl viologen or benzyl viologen was followed and compared with the corresponding reduction reactions of the "resting" oxidized enzyme. Reduction by dithionite is relatively slow, but the rate of reduction is greatly increased by addition of cytochrome c or the viologens, which are even more effective than cytochrome c on a molar basis. 3. Profound differences between the transient kinetics of the reduction of the two oxidized oxidase derivatives were observed. The results are consistent with a direct reduction of cytochrome a followed by an intramolecular electron transfer to cytochrome a3 (k1obs = 7.5 s-1 for the oxygen-pulsed oxidase). 4. The spectrum of the oxygen-pulsed oxidase formed within 5 ms of the mixing closely resembles that of the "oxygenated" compound, but there were small differences between the two spectra.

Animals↗