Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.99.3 (diaphorase)
 5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A mutant of Neurospora crassa (cni-1) has been isolated that has two pathways of mitochondrial respiration. One pathway is sensitive to cyanide and antimycin A, the other is sensitive only to salicyl hydroxamic acid. Respiration can proceed through either pathway and both pathways together in this mutant account for greater than 90% of all mitochondrial respiration. The cni-1 mutation segregates as a nuclear gene in crosses to other strains of Neurospora. Absorption spectra of isolated mitochondria from cni-1 show typical b- and c-type cytochromes but the absorption peaks corresponding to cytochrome aa(3) are not detectable. Extraction of soluble cytochrome c-546 from these mitochondria followed by reduction with ascorbate reveals a new absorption peak at 426 nm that is not present in wild-type mitochondria. This peak may be due to an altered cytochrome oxidase with abnormal spectral properties. Mitochondria from cni-1 have elevated levels of succinate-cytochrome c reductase but reduced levels of nicotinamide adenine dinucleotide reduced form cytochrome c reductase and of cyanide- and azide-sensitive cytochrome c oxidase. These studies suggest that the cni-1 mutation results in the abnormal assembly of cytochrome c oxidase so that the typical cytochrome aa(3) spectrum is lost and the enzyme activity is reduced. As a consequence of this alteration, a cyanide-insensitive respiratory pathway is elaborated by these mitochondria which may serve to stimulate adenosine 5'-triphosphate production via substrate level phosphorylation by glycolysis and the Krebs cycle.
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PMID:Altered mitochondrial respiration in a chromosomal mutant of Neurospora crassa. 435 89

The monoiodotyrosine 74, formyltryptophan 59, mononitrotyrosine 67, and carboxymethylmethionine 80 derivatives of horse cytochrome c are defective in their ability to accept electrons from the succinate-cytochrome c reductase system, while their reactions with purified cytochrome c oxidase are essentially those of the native protein. The 4-nitrobenzo-2-oxa-1,3-diazole derivative of lysine 13 of horse cytochrome c and the bis-phenylglyoxal derivative of arginine 13 of Candida krusei cytochrome c have the opposite properties, in that they are readily reduced by the succinate-cytochrome c reductase (EC 1.3.99.1) system but are defective in their capability of transferring electrons to cytochrome c oxidase (EC 1.9.3.1). We conclude that electrons from mitochondrial cytochrome c reductase are transmitted to ferricytochrome c by a different pathway than electrons from ferrocytochrome c to cytochrome c oxidase. The present results are compatible with the concept that the mechanism of reduction involves an aromatic ring channel comprising residues 74, 59, 67, and 80, leading from the "left back" part of the protein to the heme iron. On the other hand, since residue 13 is immediately above the edge of the heme that is at the "front surface" of the molecule, we suggest that the electron leaves ferrocytochrome c to cytochrome c oxidase by way of the edge of pyrrole ring II or the adjacent surface-located sulfur of cysteinyl residue 17, which is thioether bonded to the heme. On this basis, the sites of electron entry and exit in cytochrome c would appear to be some 110 degrees of arc away from each other along the surface of the protein, explaining several previously observed phenomena.
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PMID:Separate intramolecular pathways for reduction and oxidation of cytochrome c in electron transport chain reactions. 436 86

The mammalian-type cytochrome c of the basidiomycete Ustilago sphaerogena contains in a single polypeptide chain of 107 residues, two histidine residues located at positions 18 and 33, and one methionine residue situated at position 80 (Bitar et al., 1972). The reaction of Ustilago ferricytochrome c with bromoacetate at neutral pH resulted in the modification of histidine-33, but not of histidine-18 or of the invariant methionine residue. The activities of Ustilago cytochrome c with mitochondrial cytochrome c oxidase and with NADH-cytochrome c reductase were unaltered by the modification. The equilibrium constants for the formation of low-spin complexes of the ferrihaem octapeptide of horse cytochrome c (residues 14-21, including the haem bound covalently to cysteines 14 and 17) with imidazole, N(2)-acetylhistidine and monocarboxymethyl derivatives of N(2)-acetylhistidine were determined spectrophotometrically. Alkylation of the imidazole side-chain group of N(2)-acetylhistidine resulted in a marked decrease in its ability to form low-spin ferrihaem complexes. These results indicate that in Ustilago ferricytochrome c in solution histidine-33 is not involved in the central co-ordination complex. Since side-chain groups of residues other than histidine and methionine do not appear to be involved in the central complexes of other mammalian-type cytochromes c (Hettinger & Harbury, 1964, 1965; Myer & Harbury, 1965) it is likely that in Ustilago ferricytochrome c in solution at neutral pH, the side-chain groups of histidine-18 and methionine-80 are involved in the central co-ordination complex. The latter is stable over the pH range 2.6-8.4.
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PMID:Haem ligands of the ferricytochrome c of Ustilago sphaerogena. 436 59

A 3-week-old girl with failure to thrive and cardiomegaly died of cardiac arrest at age 4 weeks. Morphologic studies of the heart showed enlarged muscle fibers with large accumulations of mitochondria, characteristic of histiocytoid cardiomyopathy. Biochemical studies showed markedly decreased succinate-cytochrome c reductase and rotenone-sensitive NADH-cytochrome c reductase activities, while other mitochondrial enzymes were normal. In isolated mitochondria, cytochrome spectra showed a severe defect of reducible cytochrome b and a less marked defect of cytochrome cc1, while the content of cytochrome aa3 (cytochrome c oxidase) was normal. Histiocytoid cardiomyopathy appears to be due to a defect of complex III (reduced coenzyme Q-cytochrome c reductase) in the respiratory chain of heart mitochondria.
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PMID:Histiocytoid cardiomyopathy of infancy: deficiency of reducible cytochrome b in heart mitochondria. 609 33

We have studied a 17-year-old girl with lactic acidosis (3-18 mEq/liter) and progressive muscle weakness since 9 years of age. Morphological findings in muscle were of a typical ragged red myopathy with multiple collections of bizarre mitochondria, some containing paracrystalline inclusions. The carnitine content of serum and muscle was normal, as were the activities of carnitine palmitoyltransferase, carnitine octanoyltransferase, and carnitine acetyltransferase in the patient's muscle. Measurement of the enzymes of oxidative phosphorylation in both crude muscle homogenates and mitochondrial fractions showed close to normal activities of cytochrome c oxidase, succinate dehydrogenase, and ATPase. In contrast, succinate cytochrome c reductase activity was greatly reduced in the patient, being 0.035 mumol/min/g tissue in whole muscle (controls 1.16 +/- 0.47 mumol/min/g tissue) and 8 nmol/min/mg protein in the mitochondria (control, 340 nmol/min/mg protein). Rotenonesensitive NADH-cytochrome c reductase was also undetectable in the patient's mitochondria. Spectral analysis of cytochromes showed decrease of reducible cytochrome b to 16% of the control. These results indicate a defect of ubiquinol-cytochrome c reductase or the cytochrome bc1 segment (complex III) of the electron transport chain. Antibody-binding studies of the individual components of complex III showed additional deficiencies of core proteins I and II and peptide VI, indicating a more widespread defect of complex III than was evident from spectral analysis and enzyme activity measurements alone. Urine organic acid analysis after fasting and following a medium chain triglyceride load showed unusually high levels of lactate and 3-hydroxybutyrate, lower than expected levels of acetoacetate and dicarboxylic acids, and the presence of several other metabolites suggesting a disturbed citric acid cycle and redox state.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Lactic acidosis and mitochondrial myopathy associated with deficiency of several components of complex III of the respiratory chain. 609 35

Mitochondrial respiration can be inhibited in vitro by a complex of exotoxins elaborated by Staphylococcus aureus. This complex, designated Succinic Oxidase Factor, consists of two components, one of which (A) has a molecular weight of 75,000, is heat-stable, and interferes with cytochrome c oxidase and the other (B) has a molecular weight of 42,000, is heat-labile, and interferes with succinate-cytochrome c reductase. Each component can be separated by Sephadex G200 chromatography and purified by isoelectric focussing. Component A focussed at pH 3.4 and component B focussed at pH 4.5. Antibody prepared in rabbits to Succinic Oxidase Factor could neutralise the biological activities of each component separately or the whole complex and could react serologically with each component in an agar precipitation test.
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PMID:Purification and properties of succinic oxidase factor, an extracellular product of Staphylococcus aureus. 609 43

(1) Biopsies from the gastrocnemius muscle of patients with Duchenne dystrophy were partitioned into a myofibrillar plus nuclear fraction, a mitochondrial fraction and a supernatant fraction. The fractions were assayed for mitochondrial enzymes and protein, in order to obtain information about the integrity of mitochondrial structure and function. Muscles from boys and adults without neuromuscular disease were treated likewise. (2) In adults, muscle possesses a significantly higher specific activity (on protein basis) of monoamine oxidase and rotenone-insenitive NADH-cytochrome c reductase (RINCR) than in boys. In childhood, monoamine oxidase activity increases with age. At the age of 5 yr, the specific activity is 50% of the adult value. RINCR activity is constant in childhood. With adolescence it increases from 20 +/- 2 (SEM) to 35 +/- 6 mumoles cytochrome c reduced per min per g protein, and it remains at this level. Palmitoyl-CoA synthetase activity remains constant with age. (3) In Duchenne dystrophy the extractable protein content from muscle is decreased to 75%. The specific activities of the matrix enzymes propionyl-CoA carboxylase and glutamate dehydrogenase are 1.8 and 2.8 times increased, the inner membrane enzyme cytochrome c oxidase is 2.8 times increased, the inner membrane enzyme cytochrome c oxidase is 2.8 times increased. Of the outer membrane enzymes RINCR is 2.0 times increased, while palmitoyl-CoA synthetase is not changed in acitivity. In Duchenne dystrophy monoamine oxidase activity also increases with age. In part this may be due to mitochondria from adipose tissue and macrophages, which are increasingly present in older patients. The specific activities of enzymes with a predominant cytosolic localisation, creatine kinase and adenylate kinase, are increased by a factor of 1.5 and 1.7. (4) The subcellular distribution of the studied enzymes in human skeletal muscle was found to be similar as in animal studies. In mitochondrial fractions from Duchenne patients the recoveries of the following enzymes are decreased: glutamate dehydrogenase (from 25 to 9%), creatine kinase (1.1-0.66%), adenylate kinase (0.44-0.22%), hexokinase (7.1-2.7%), monoamine oxidase (36-21%), RINCR (30-17%), and palmitoyl-CoA synthetase (40-21%). The recoveries of last 3 mitochondrial outer membrane enzymes in the supernatant fractions are correspondingly increased. These results indicate an increased fragility of the mitochondrial membranes in dystrophic muscles. (5) The reported changes are clearly evident in a one-year-old patient, which indicates that the mitochondria are involved early in the disease process.
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PMID:Early changes of muscle mitochondria in Duchenne dystrophy. Partition and activity of mitochondrial enzymes in fractionated muscle of unaffected boys and adults and patients. 624 85

The isolated complexes of ferricytochrome c with cytochrome c oxidase, cytochrome c reductase (cytochrome bc1 or complex III), and cytochrome c1 (a subunit of cytochrome c reductase) were investigated by the method of differential chemical modification (Bosshard, H.R. (1979) Methods Biochem. Anal. 25, 273-301). By this method the chemical reactivity of each of the 19 lysyl side chains of horse cytochrome c was compared in free and in complexed cytochrome c and binding sites were deduced from altered chemical reactivities of particular lysyl side chains in complexed cytochrome c. The most important findings follow. 1. The binding sites on cytochrome c for cytochrome c oxidase and cytochrome c reductase, defined in terms of the involvement of particular lysyl residues, are indistinguishable. The two oxidation-reduction partners of cytochrome c interact at the front (exposed heme edge) and top left part of the molecule, shielding mainly lysyl residues 8, 13, 72 + 73, 86, and 87. The chemical reactivity of lysyl residues 22, 39, 53, 55, 60, 99, and 100 is unaffected by complex formation while the remaining lysyl residues in positions 5, 7, 25, 27, 79, and 88 are somewhat less reactive in the complexed molecule. 2. When bound to cytochrome c reductase or to the isolated cytochrome c1 subunit of the reductase the same lysyl side chains of cytochrome c are shielded. This indicates that cytochrome c binds to the c1 subunit of the reductase during the electron transfer process.
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PMID:Comparison of the binding sites on cytochrome c for cytochrome c oxidase, cytochrome bc1, and cytochrome c1. Differential acetylation of lysyl residues in free and complexed cytochrome c. 624 81

Methyl-4-azidobenzoimidate was reacted with horse heart cytochrome c to give a photoaffinity-labeled derivative of this heme protein. The modified cytochrome c bound to cytochrome c-depleted mitochondria with the same Kd as native cytochrome c and restored oxygen uptake to the same extent. Irradiation of cytochrome c-depleted mitochondrial membranes with 3- to 4-fold excess of photoaffinity-labeled cytochrome c over cytochrome c oxidase resulted in covalent binding of the derivative to the membranes. Fractionation of the irradiated mitochondria in the presence of detergents and salts followed by chromatography on an agarose Bio-Gel-A-5m showed that the labeled cytochrome c was bound covalently to succinate-cytochrome c reductase. The covalently bound cytochrome c was active in mediating electron transfer between its reductase and oxidase. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the succinate-cytochrome c reductase containing photoaffinity-labeled 125I-cytochrome c showed that the reductase contained a protein binding site for cytochrome c. It is suggested that cytochrome c1 is the most likely site for the cytochrome c binding in mitochondria in situ.
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PMID:Interactions of cytochrome c with mitochondrial membranes. Binding to succinate-cytochrome c reductase. 625 50

There exists considerable controversy regarding membrane topography in vesicles derived by osmotic lysis of spheroplasts of Gram-negative bacteria. It has been reported by others that bee venom can be used to quantitate the portion of a heterogeneous vesicle population with an inside-out orientation by determining the degree of loss of crypticity of NADH dehydrogenase activity. We have demonstrated that a major component of bee venom, melittin, causes an increase in the activity of several different respiratory enzymes in isolated membrane vesicles of Paracoccus denitrificans. The degree of stimulation produced by melittin is dependent upon (i) the nature of the respiratory substrates, (ii) the pH, (iii) the presence of Mg2+, (iv) the melittin: membrane protein ratio, and (v) the growth history of the cells from which the membrane vesicles were derived. Melittin-induced enhancement of TMPD:ascorbate and cytochrome c oxidase activities cannot be accounted for by increased accessibility of nonpermeant substrate to the interior of the vesicle. The stimulatory effect of melittin may rely in part on its ability to alter the proton permeability of the membrane thereby abolishing respiratory control. Collectively these observations call into question the usefulness of bee venom melittin in quantitative analyses of membrane topography. These results are consistent with the postulated existence of a homogeneous vesicle population in which the topography of the NADH dehydrogenase is different from that of the intact cell.
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PMID:The use of bee venom melittin to assess the topography of membrane vesicles derived from Paracoccus denitrificans. 625 50


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