Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q8NEX9 (reductase)
 26,410 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activity of methemoglobin reductase was studied in human red cells treated with methylguanidine and guanidinosuccinic acid in concentrations similar to those in plasma of patients with chronic renal failure. Enzyme activity was measured with Richterich technique following an incubation at 37 degrees C for three hours. Results have shown that methylguanidine in concentration of 5.4 x 10(-5) mol/l decreases activity of methemoglobin reductase in human red cells on average by 13.9%. Higher concentrations potentiate this effect. Similar changes in methemoglobin reductase activity were noted after introduction of guanidine-succinic acid into the mixture. This agent in concentration 5.6 x 10(-5) mol/l inhibited activity of the tested enzyme by 34.2% on average. Combined methylguanidine in concentration of 5.4 x 10(-5) mol/l and guanidine-succinic acid in concentration of 2.8 x 10(-5) mol/l inhibited methemoglobin reductase activity by 33.0% on average. It may be suggested, that methylguanidine and guanidine-succinic acid being low molecular uremic toxins may significantly decrease methemoglobin reductase activity in red cells of patients with chronic renal failure.
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PMID:[Effect of methylguanidine and guanidine succinic acid on methemoglobin reductase activity in human red cells]. 184 32

The effect of temperature on the activities of cytoplasmic and membrane-bound fractions of NADH-cytochrome beta 5 reductase on the total activity of methemoglobin reductase in intact human erythrocytes was studied within the temperature range of 20-50 degrees C. The above three activities showed a break in the Arrhenius plots at 42 degrees C which was attributed to irreversible inactivation of the enzymes. Thermal inactivation of methemoglobin reductase in erythrocytes was found to increase the methemoglobin content concomitantly with a decrease in the osmotic stability and activation of spontaneous cell hemolysis.
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PMID:[Dependence of human erythrocyte methemoglobin reductase on temperature]. 187 46

Two protein components having a NADPH-dependent methemoglobin reductase activity were purified to electrophoretic homogeneity from the erythrocytes of the bullfrog, Rana catesbeiana. Their molecular properties were investigated. The components were separated by isoelectric focusing, having discrete bands of pI 5.0 and 7.5, respectively. The pI 5.0 component, designated F-5.0, was faint yellow, with a broad absorption in the range of 400-450 nm, while the pI 7.5 component, designated F-7.5, was colorless and did not absorb in that range. The molecular weight was estimated to be 22,000 for both components by gel filtration and SDS-PAGE. When F-5.0 was subjected to isoelectric focusing repeatedly, the protein part of that component gradually moved to and refocused at pH 7.5, leaving a yellow color at acidic pH. Both F-5.0 and F-7.5 were highly specific for NADPH and had the same kinetic properties in catalyzing the reduction of MB, DCPIP, FMN, or FAD, and that of methemoglobin or cytochrome c in the presence of a certain dye. They were also indistinguishable from one another in their amino acid compositions and were completely identical in the N-terminal sequence of 24 amino acid residues. These findings strongly suggest that the two components can be attributed to the same enzyme molecule, carrying an identical protein moiety but interacting differently with some unidentified biological pigments, and that they are equivalent in their molecular and kinetic properties to the NADPH-dependent enzyme(s) occurring in human erythrocytes.
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PMID:Purification and characterization of NADPH-dependent methemoglobin reductase from the nucleated erythrocytes of bullfrog, Rana catesbeiana. 217 27

In twenty five patients who presented the cutaneous form of loxoscelism, serum haptoglobin and lactic dehydrogenase, erythrocyte glucose-6-phosphate dehydrogenase, glutathione reductase, glutathione peroxidase, methemoglobin, bilirubin and reticulocytes were investigated after bite. No hemolysis was detected but an increase in methemoglobin was found in 54% of the cases; in 7% it was between 1.1% and 2%, in 27% it ranged from 2.1% to 4%, and in 20% from 4.1% to 8%. Blood samples of a normal, blood group 0 individual and of a patient who exhibited methemoglobinemia after Loxosceles bite were incubated separately with antisera against Loxosceles gaucho, Crotalus terrificus, Bothrops jararaca, with Loxosceles gaucho venom and 0.3% phenol. No methemoglobin was found after 1, 4, 8 and 15 days in both sets of samples. At the 25th day all the samples, including the controls, exhibited similar methemoglobin reductase decrease. The data suggest that the methemoglobinemia which occurs in 50% of the patients probably arises from in vivo venom metabolism, inasmuch as the crude venom does not induce methemoglobinemia.
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PMID:Methemoglobinemia associated with loxoscelism. 225 27

Topical 20% benzocaine (Hurricaine, Beutlich, Inc., Niles, Ill.) spray is frequently used for oral anesthesia before upper endoscopy. Side effects attributed to this agent are exceedingly rare. The author reports one of these rare complications, drug-induced methemoglobinemia, in a patient with methemoglobin reductase deficiency. The mechanisms for the development of methemoglobinemia and its treatment are reviewed.
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PMID:Methemoglobinemia as a complication of 20% benzocaine spray for endoscopy. 229 80

A total of 17 cases of anomalous hemoglobin M (Hb M) were detected among subjects of varying nationalities in different regions of the USSR. The methods used for identification of Hb M Saskatoon, Hb M Boston, Hb M Iwate, Hb M Hyde Park have been described, among them--electron paramagnetic resonance. Spectral characteristics, electrophoretic mobility of these Hb in pH gradient, reaction with cyanides, thermal stability, in vitro reduction with methemoglobin reductase, isolated from donor's red blood cells, have been investigated. The functional parameters (log P50 and n) have been determined for hemolysates containing anomalous hemoglobin, as well as for chromatographically pure fractions of anomalous hemoglobins. The importance of the proper diagnosis of hemoglobinosis M has been stressed.
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PMID:[Hereditary cyanosis caused by the presence of abnormal hemoglobin M in the blood: its detection, identification and properties]. 236 89

We have examined aspects of methemoglobin (metHb) reduction in sickle and in thalassemic red blood cells (RBCs). NADH metHb reductase activity in sickle and thalassemic RBCs was significantly increased compared with normal RBCs. Because in vitro enzyme activity does not necessarily represent in vivo activity, we measured the rate of metHb reduction in intact RBCs. Intact thalassemic RBCs demonstrated a significantly increased rate of metHb reduction compared with normal RBCs. In contrast, intact sickle RBCs had a rate of metHb reduction that was similar to normal RBCs and significantly decreased relative to high reticulocyte RBCs of equivalent cell age. To determine the mechanism for the relative impairment of metHb reduction in sickle RBCs, we measured intraerythrocytic NADH, a cofactor in the metHb reduction reaction. Thalassemic RBCs had a significantly increased NADH content relative to normal RBCs. In contrast, sickle RBCs did not have an increase in NADH content. Furthermore, incubating normal RBCs under conditions that increase the NADH content resulted in an increased rate of metHb reduction. In contrast, conditions that decrease the NADH content in normal RBC resulted in a decreased rate of metHb reduction. These data and other results suggest that metHb reduction in intact RBCs is dependent on NADH content, and that the impaired metHb reduction rate in sickle RBCs may be a result of a lack of increase in NADH content. The dependence of metHb reduction on RBC NADH content and the ability to manipulate NADH content in vitro suggest a new strategy for decreasing oxidant damage to sickle RBCs in vivo.
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PMID:Impaired erythrocyte methemoglobin reduction in sickle cell disease: dependence of methemoglobin reduction on reduced nicotinamide adenine dinucleotide content. 239 9

Among nitrogen oxides, NO and NO2 are free radicals and show a variety of biological effects. NO2 is a strongly oxidizing toxicant, although NO, not oxidizing as NO2, is toxic in that it interacts with hemoglobin to form nitrosyl- and methemoglobin. Nitrosylhemoglobin shows a characteristic electron spin resonance (ESR) signal due to an odd electron localized on the nitrogen atom of NO and reacts with oxygen to yield nitrate and methemoglobin, which is rapidly reduced by methemoglobin reductase in red cells. NO was found to inhibit the reductase activity. Part of NO inhaled in the body is oxidized by oxygen to NO2, which easily dissolves in water and converts to nitrite and nitrate. The nitrite oxidizes oxyhemoglobin autocatalytically after a lag. The mechanism of the oxidation, particularly the involvement of superoxide, was controversial. The stoichiometry of the reaction has now been established using nitrate ion electrode and a methemoglobin free radical was detected by ESR during the oxidation. Complete inhibition of the autocatalysis by aniline or aminopyrine suggests that the radical catalyzes conversion of nitrite to NO2, which oxidizes oxyhemoglobin. Recently NO was shown to be one of endothelium-derived relaxing factors and the relaxation induced by the factor was inhibited by hemoglobin and potentiated by superoxide dismutase.
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PMID:The interaction between nitrogen oxides and hemoglobin and endothelium-derived relaxing factor. 255 83

During investigation of chronic cyanosis in a 25 year old male, after excluding pulmonary and cardiac causes, methemoglobinemia was suspected. Investigation of the activity of methemoglobin reductase clenched the diagnosis of homozygous cytochrome b5 reductase deficiency in a case of recessive congenital methemoglobin type I (absence of neurologic symptoms).
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PMID:Congenital cyanosis due to methemoglobin reductase deficiency: first reported Tunisian case. 258 7

The purification to homogeneity of the membrane-bound NADH-cytochrome-b5 reductase from erythrocytes of the sipunculid, Phascolopsis gouldii is reported. This highly purified reductase has allowed more detailed characterizations of its molecular and kinetic properties than was possible in a previous study (Utecht, R.E. and Kurtz, D.M., Jr. (1988) Biochim. Biophys. Acta 953, 164-178). The reductase has a molecular weight of 34,000 and contains FAD as the prosthetic group. In aqueous solution containing 0.5 vol% Triton X-100, the reductase forms an aggregate of Mr approximately 220,000. A higher purity preparation of P. gouldii erythrocyte b5 was also obtained. The combination of purified, solubilized reductase and cytochrome b5 was shown to catalyze the quantitative two-electron reduction of [Fe(III),Fe(III)]methemerythrin to [Fe(II),Fe(II)]deoxyhemerythrin by NADH. The P. gouldii NADH-cytochrome b5 reductase is the first from hemerythrin-containing erythrocytes to be purified and characterized. This methemerythrin reduction system appears to be analogous to methemoglobin reductases from vertebrate erythrocytes.
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PMID:Purification and properties of a membrane-bound NADH-cytochrome-b5 reductase from erythrocytes of the sipunculid worm, Phascolopsis gouldii. 259 3


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