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:1.6.99.3 (diaphorase)
5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A primary objective of the present study has been to determine the changes which occur in Rana catesbeiana liver organelle membranes during thyroxine-induced metamorphosis. To this end, enzyme and cytochrome profiles were determined for mitochondria, microsomes, and nuclear membrane fractions isolated from livers of R. catesbeiana tadpoles which had been fasted for 6 days at 15 +/- 0.5 degrees and then immersed in thyroxine, 2.6 X 10(-8) M, for periods of up to 12 days at 23.5 +/- 0.4 degrees. The ratio of total succinate-cytochrome c reductase activity in the initial homogenate fraction to the total activity of this mitochondrial "marker" enzyme recovered in the final mitochondrial fraction remained constant, approximately 0.5, throughout the course of thyroxine treatment; however, after a 3- to 4-day latency the mitochondrial protein mass recovered per unit mass of initial homogenate protein was found to increase significantly (approximately 2-fold by Day 10 of thyroxine treatment). A similar increase was also observed in the yield of microsomal, but not nuclear membrane, protein mass as a function of thyroxine treatment. Prolonged thyroxine treatment (12 days) resulted in approximately 50% decreases in tadpole liver homogenate and microsomal NADH-cytochrome c reductase specific activities; in contrast, mitochondrial and nuclear membrane NADH-cytochrome c reductase specific activities were not altered under the same conditions. In addition, homogenate and microsomal NADPH-cytochrome c reductase specific activities were found to have increased significantly after 12 days of thyroxine treatment; however, the specific activity of NADPH-cytochrome c reductase in the mitochondrial fraction was unchanged. It was also observed that thyroxine treatment resulted in increases in homogenate and microsomal glucose-6-phosphatase specific activities, whereas the mitochondrial as well as nuclear membrane glucose-6-phosphatase specific activities remained unchanged. Furthermore, in contrast to homogenate and mitochondrial monoamine oxidase specific activities, which decreased 30 and 40%, respectively, as a consequence of thyroxine treatment (12 days), the succinate-cytochrome c reductase and oligomycin-sensitive Mg2+ ATPase specific activities determined for these fractions increased significantly. In all instances, changes as a result of thyroxine treatment in membrane-localized homogenate or organelle enzyme specific activities were apparent only after a 3- to 4-day initial latent period. The in vitro effects of thyroxine (10(-10) - 10(-5) M) on the membrane-localized enzyme activities examined in this study were either negligible or, as in the case of mitochondrial succinate-cytochrome c reductase and microsomal NADH-cytochrome c reductase, opposite to the changes observed in response to in vivo thyroxine treatment, with the exception of microsomal NADPH-cytochrome c reductase activity which was enhanced approximately 2-fold by 10(-5) M thyroxine...
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PMID:Alterations in enzyme and cytochrome profiles of Rana catesbeiana liver organelles during thyroxine-induced metamorphosis. Changes in membrane-localized phosphohydrolases, oxidoreductases, and cytochrome levels in response to in vivo thyroxine administration. 18 3

Pieces of liver (in vitro ischemia) and isolated microsomes were subjected to incubation at 4 degrees C and 37 degrees C for various time intervals. The effects on microsomal protein, phospholipids, and cholesterol and on microsomal phosphatases and electron transport enzymes were followed as a functional of time and temperature. NADH-cytochrome c reductase was very labile and was completely inactivated by 1 h, whereas G6Pase lost 50% of its activity after 2 h at 37 degrees C. IDPase and NADPH-cyt. c red. were of intermediate susceptibility whereas cytochromes b5 and P-450 were the most stable enzymes assayed. After 24 h of incubation of isolated microsomes at 37 degrees C there was no significant detachment of membrane components (protein, PLP or cholesterol), indicating that the inactivation of the enzymes was not primarily attributable to their solubilization. Instead, experiments with 14C-leucine and 14C-glycerol prelabeled microsomes demonstrated that the proteins detached from microsomes during incubation originated mainly from the intravesicular space due to repture of the microsomal membranes. The addition of a lysosomal extract during incubation did not alter either the rate of inactivation of the enzymes or the proportion of solubilized membrane components indicating that attack from the outside by proteolytic enzymes is not the mechanism for enzyme inactivation. There was no apparent correlation between the rates of inactivation of enzymes in vitro and their calculated half-lives in vivo or their postulated intramembranous localization. Ultrastructurally, enzyme inactivation was initially associated with alterations of the microsomal membranes, such as vesicle aggregation, membrane rupture, loss of unit membrane structure, and subsequently, thickening of membranes and transformation of the microsomes into nonrecognizable amorphous material.
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PMID:Effect of storage and in vitro ischemia on the ultrasture of microsomal membranes and on microsomal enzymes. 18 24

The dehydrogenation reaction of cholest-7-en-3beta-ol (I) to cholesta-5,7-dien-3beta-ol (II) in the presence of NADH was studied in rat liver microsomes and in microsomal acetone powder preparations, using [3alpha-3H]cholest-7-en-3beta-ol. It was found that the reaction was inhibited by menadione, adenosine diphosphate, potassium ferricyanide, and cytochrome c while p-cresol had no effect. These results indicated the participation of a microsomal electron transport system in the dehydrogenation of cholest-7-en-3beta-ol. The conversion of cholest-7-en-3beta-ol to cholesta-5,7-dien-3beta-ol was also observed in the absence of NADH when ascorbic acid was included in the incubation mixture. However, the ascorbic acid-catalyzed dehydrogenation was not inhibited by potassium ferricyanide. Immunological evidence that microsomal cytochrome b5 is involved in the dehydrogenation of (I) to (II) was obtained. Antibodies specific for rat liver microsomal cytochrome b5 were elicited in rabbits. The anticytochrome b5 immunoglobulin fraction inhibited rat liver microsomal NADH-cytochrome c reductase but not NADPH-cytochrome c reductase. Also, the extent of reduction of cytochrome b5 was not affected by the antibodies. The conversion of (I) to (II) by rat liver microsomes was inhibited (73%) by anticytochrome b5 immunoglobulin at a ratio of microsomal protein:immunoglobulin of 1:5.6. These results are consistent with the participation of microsomal cytochrome b5 in the introduction of the C-5 double bond in cholesterol biosynthesis. A close analogy of the microsomal dehydrogenation of fatty acids and of cholest-7-en-3beta-ol is apparent and this suggests a possible similarity in the mechanisms of the two reactions.
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PMID:Mechanism of C-5 double bond introduction in the biosynthesis of cholesterol by rat liver microsomes. 19 22

Microsomal NADH-cytochrome b5 reductase is an amphiphilic protein consisting of a hydrophilic (catalytic) region and a hydrophobic (membrane-binding) segment. Digestion of the reductase purified from rabbit liver microsomes with carboxypeptidase Y (CPY), but not with aminopeptidases, resulted in the abolishment of the capacities of the reductase to bind to phosphatidylcholine liposomes and to reconstitute an active NADH-cytochrome c reductase system upon mixing with cytochrome b5. The NADH-ferricyanide reductase activity of the flavoprotein was, however, inactivated only slightly by the CPY digestion. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and amino acid analyses indicated that the CPY treatment removed about 30 amino acid residues from the tcooh terminus of the reductase and that about 70% of the amino acids released were hydrophobic. It is concluded that the hydrophobic region of the reductase, responsible for both membrane binding and effective reconstitution of NADH-cytochrome c reductase activity, is located at the COOH-terminal portion of the molecule. No NH2-terminal residue could be detected in the intact and CPY-modified reductase preparations. The location of the hydrophobic, membrane-binding segment at the COOH-terminal end and the masked NH2 terminus have also been reported for cytochrome b5, another microsomal membrane protein.
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PMID:Reduced nicotinamide adenine dinucleotide-cytochrome b5 reductase: location of the hydrophobic, membrane-binding region at the carboxyl-terminal end and the masked amino terminus. 21 Jul 82

Myocardial ischemia was produced for 2 hours by coronary ligation in 11 dogs pretreated with methylprednisolone (MP, 30 mg/kg). Myocardial blood flow (MBF) was measured with microspheres (15 micrometer) in each tissue sample used for enzymatic analysis. Homogenates of these tissue samples were separated by ultracentrifugation into lysosome-rich and microsomal fractions and were analyzed for N-acetyl-beta-glusosaminidase (NAGA), beta-glucuronidase (beta-gluc), rotenone-insensitive-NADH-cytochrome c reductase (RINCR), and cytochrome oxidase. The enzymatic data from centrifugal fractions were grouped according to MBF values for statistical analysis of inter-group effects of ischemia. Significant losses (P less than 0.001) of NAGA and beta-gluc were seen in all MP-treated lysosome-rich particulate fractions that were isolated from zones demonstrating MBF values less than 25% of control (L-ischemia). Similar significant losses (P less than 0.001) of RINCR were seen in microsomal fractions from L-ischemia zones. Samples with MBF values greater than 25% but less than 75% of control (M-ischemia) also demonstrated significant decreases of lysosomal and microsomal enzymatic activity in specific fractions. When the data of the above MP-treated group were compared with the untreated control group, no significant intergroup effects of treatment with MP were observed. In addition, enzymatic data (NAGA, RINCR) were normalized prior to performing linear regression analyses; percent loss of particulate enzymatic activity was plotted against percent decrease in MBF. The effects of 2 hours of ischemia on the above biochemical parameters were comparable between untreated and MP-treated groups. Finally, when myocardial samples were grouped according to similar levels of MBF, statistical analysis using the general linear models procedure revealed no beneficial effect of MP treatment on changes in lysosomal hydrolases, microsomal RINCR, or latency of lysosomes.
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PMID:Lack of effect of methylprednisolone on lysosomal and microsomal enzymes after two hours of well-defined canine myocardial ischemia. 21 3

The effects of vitamin E deficiency on membrane integrity were studied by examining the temperature dependence of membrane-bound enzyme activities in liver mitochondria and microsome and in muscle sarcoplasmic reticulum. In vitamin E-deficient rabbits, the specific activities at 37 degrees of mitochondrial oligomycin-sensitive ATPase (EC 3.6.1.3), beta-hydroxybutyrate dehydrogenase (EC 1.1.1.30), and microsomal glucose-6-phosphatase (EC 3.1.3.9) were increased, whereas those of microsomal NADH cytochrome C reductase (EC 1.6.99.3) and sarcoplasmic reticulum Ca-ATPase were reduced in comparison to control rabbits. Arrhenius plots of activity against temperature yielded a linear plot over the range 10 to 40 degrees in the case of beta-hydroxybutyrate dehydrogenase, NADH cytochrome C reductase and Ca-ATPase, and multiple discontinuities for glucose-6-phosphatase and oligomycin-sensitive ATPase. In control rabbits, all five enzymes showed a single discontinuity in the Arrhenius plot over the range 16 to 19 degrees. These results reflect changes in the microenvironment of membrane-bound enzymes as a consequence of vitamin E depletion.
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PMID:Effects of vitamin E deficiency on the activities of lipid-requiring enzymes in rabbit liver and muscle. 22 Mar 97

By means of a preparation technique based on the discontinuous sucrose density gradient, subcellular fractions were isolated from guinea pig intestinal smooth muscle cells. A fraction which distributed to a 33% sucrose layer showed relatively high activities of 5'-nucleotidase, Na+ . K+-ATPase and ouabain sensitive Na+ . K+-ATPase. The fraction had a low NaN3 sensitive Mg2+-ATPase activity. On the other hand, the high activity of glucose-6-phosphatase showed a broad distribution. Though the sucrose density gradient proceeded over a series of the fine layers, cross-contamination of microsome into the 33% sucrose fraction was not reduced. To reduce microsomal cross-contamination, another procedure was employed. The homogenization time of 77000 xg sediment to be layered on the top of the sucrose density gradients was prolonged. This procedure did not change the distribution of K+ activated p-nitrophenylphosphatase, K+ activated ouabain sensitive p-nitrophenylphosphatase and ouabain sensitive Na+ . K+-ATPase activities. The peak of NADH cytochrome c reductase activity was shifted to a 38% sucrose fraction from a 33% sucrose fraction and the activity of this marker enzyme in the 33% sucrose fraction decreased to 60% of that of the prior procedure.
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PMID:[Examination of plasma membrane-enriched fraction from guinea pig intestinal smooth muscle by means of some marker enzymes (author's transl)]. 23 74

Purified rat liver NADPH-cytochrome c reductase supports iodination of tyrosine in a system including NADPH, cytochrome c and thyroid perioxidase. Catalase inhibits the iodination of tyrosine, while superoxide dismutase has no effect. Antibody developed in the rabbit against purified rat liver NADPH-cytochrome c reductase inhibits both reduction of cytochrome c and tyrosine iodination supported by the enzyme. The antibody forms a single precipitation line with thyroid extract, and inhibits NADPH cytochrome c reductase activity of the thyroid. The antibody partially inhibits iodination in a thyroid mitochondrial-microsomal fraction, but does not inhibit NADH-dependent iodination. The immunochemical studies indicate the participation of NADPH-cytochrome c reductase in thyroidal H2O generation, and the independent existence of NADPH-dependent and NADH-dependent H2O2 generation mechanisms in the thyroid.
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PMID:Participation of NADPH-cytochrome C reductase in thyroid hormone biosynthesis. 23 16

In the presence of Fe-3+ and complexing anions, the peroxidation of unsaturated liver microsomal lipid in both intact microsomes and in a model system containing extracted microsomal lipid can be promoted by either NADPH and NADPH : cytochrome c reductase or by xanthine and xanthine oxidase. Erythrocuprein effectively inhibits the activity promoted by xanthine and xanthine oxidase but produces much less inhibition of NADPH-dependent peroxidation. The singlet-oxygen trapping agent, 1, 3-diphenylisobenzofuran, had no effect on NADPH-dependent peroxidation but strongly inhibited the peroxidation promoted by xanthine and xanthine oxidase. NADPH-dependent lipid peroxidation was also shown to be unaffected by hydroxyl radical scavengers.. The addition of catalase had no effect on NADPH-dependent lipid peroxidation, but it significantly increased the rate of malondialdehyde formation in the reaction promoted by xanthine and xanthine oxidase. The results demonstrate that NADPH-dependent lipid peroxidation is promoted by a reaction mechanism which does not involve either superoxide, singlet oxygen, HOOH, or the hydroxyl radical. It is concluded that NADPH-dependent lipid peroxidation is initiated by the reduction of Fe-3+ followed by the decomposition of hydroperoxides to generate alkoxyl radicals. The initiation reaction may involve some form of the perferryl ion or other metal ion species generated during oxidation of Fe-2+ by oxygen.
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PMID:The mechanism of liver microsomal lipid peroxidation. 23 6

1. The effects of halothane (CF3CHBrCl), a volatile anaesthetic agent, on electron transfer in isolated rat liver microsomal preparations were examined. 2. At halothane concentrations achieved in tissues during clinical anaesthesia (1-2mM), halothane shifts the redox equilibrium of microsomal cytochrome b5 in the presence of NADPH towards the oxidized form. Halothane accelerates stoicheiometric consumption of NADPH and O2, increases the rate of reoxidation of NADH-reduced microsomal ferrocytochrom b5, but does not affect NADPH- or NADH-cytochrome c reductase activity. The enhanced microsomal electron flow seen in the presence of halothane is not diminished by CO nor is it increased by pretreatment of the animals with phenobarbital. 3. The effects of halothane are maximum in microsomal preparations isolated from animals fed on a high-carbohydrate diet to induce stearate desaturase activity. Changes in microsomal electron transfer caused by halothane are in all cases abolished by low concentrations (1-2mM) of cyanide. Microsomal stearate desaturase activity is unaffected by halothane. 4. The first-order rate constant for oxidation of membrane-bound ferrocytochrome b5 in the absence of added substrate (k1 equals 1.5 times 10(-3)A-1) is similar to that for autoxidation of purified ferrocytochrome b5(k1 equals 7 times 10(-3)S-1) the rate of autoxidation of soluble ferrocytochrome b5 is unaffected by halothane. 5. It is concluded that the effects of halothane on microsomal electron transfer are not related to cytochrome P-450 linked metabolism but rather arise from the interaction of halothane with the cyanide-sensitive factor of the stearate desaturase pathway.
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PMID:The effects of halothane on hepatic microsomal electron transfer. 23 6


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