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:1.11.1.6 (catalase)
55,569 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Ethanol metabolism in slices or homogenates of transplantable hepatocellular carcinoma HC-252 (HC-252) was 50 to 60% of the rate found in host liver slices or homogenates when they were expressed per gram of tissue wet weight and 70 to 80% of the liver when the rates were expressed per milligram of tissue protein. At 10 mM ethanol, the activities of alcohol dehydrogenase in tumor and liver supernatants were comparable. 2. Tumor microsomes did not oxidize ethanol in the presence of a NADPH-generating system, indicating the absence of the microsomal ethanol-oxidizing system and catalase-mediated peroxidation of ethanol. The HC-252 microsomes were contaminated with catalase, and acetaldehyde production occurred in the presence of a H2O2-generating system (xanthine oxidase). The virtual absence of ethanol oxidation and drug metabolism (aminopyrine demethylase and aniline hydroxylase) in HC-252 microsomes may be due to the low activities of NADPH-cytochrome c reductase, NADPH oxidase, and NADPH-dependent oxygen uptake. 3. Microsomal oxidation of ethanol was present in Morris hepatoma 5123C, a well-differentiated tumor of intermediate growth rate, while activity was negligible in microsomes from Morris hepatoma 7288CTC, a less differentiated tumor. Microsomal NADPH oxidase was present in the well differentiated tumor 5123C but was lacking in the less differentiated tumor 7288CTC. Several microsomal, mitochondrial, and cytosolic properties of HC-252 are similar to those of Morris hepatoma 7288CTC but differ from those of the more differentiated 5123C tumor and normal liver. 4. The content of mitochondrial protein in HC-252 was only 25% that of liver, and oxygen consumption per gram of tumor was only 28% that of the liver. When corrected for the mitochondrial protein content, oxygen uptake in tumor HC-252 and liver homogenates was comparable. Isolated tumor and liver mitochondria displayed comparable State 4 and 3 rates of oxygen consumption with succinate and glutamate as substrates. The activities of the reconstituted malate-aspartate and alpha-glycerophosphate shuttles were only slightly lower in isolated HC-252 mitochondria compared to liver mitochondria, when shuttles were reconstituted with purified enzymes. 5. Antimycin inhibited alcohol metabolism,and pyruvate stimulated alcohol metabolism, much less in tumor slices than in liver slices, suggesting the presence of an augmented mitochondria-independent, cytosolic mechanism for oxidizing reducing equivalents in the tumor. These factors suggest that oxidation of NADH is the limiting factor in ethanol metabolism. Whereas, in the liver mitochondrial reoxidation is predominant, in HC-252, cytosolic reoxidation of NADH also plays a major role.
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PMID:Ethanol metabolism by a transplantable hepatocellular carcinoma. Role of microsomes and mitochondria. 13 37

Thiourea and diethylthiourea, two compounds which react with hydroxyl radicals, inhibited NADPH-dependent microsomal oxidation of ethanol and 1-butanol. Inhibition by both compounds was more effective in the presence of the catalase inhibitor, azide. Inhibition by thiourea was noncompetitive with respect to ethanol in the absence of azide but was competitive in the presence of azide. Urea, a compound which does not react with hydroxyl radicals or H2O2, was without effect. Thiourea had no effect on NADH- and NADH-cytochrome c reductase, NADPH oxidase, and NADH- and NADPH-dependent oxygen uptake. Thiourea inhibited the activities of aniline hydroxylase and aminopyrine demethylase. Thiourea, but no other hydroxyl radical scavengers, e.g., dimethyl sulfoxide, mannitol, and benzoate, reacted directly with H202 and decreased H2O2 accumulation in the presence of azide. Therefore the actions of thiourea are complex because it can react with both hydroxyl radicals and H2O2. Differences between the actions of thiourea and those previously reported for dimethyl sulfoxide, mannitol, and benzoate, e.g., effects on drug metabolism, effectiveness of inhibition in the absence of azide, or kinetics of the inhibition, probably reflect the fact that thiourea reacts directly with H2O2 whereas the other agents do not. The current results remain consistent with the concept that microsomal oxidation of alcohols involves interactions of the alcohols with hydroxyl radicals generated from microsomal electron transfer.
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PMID:Effect of thiourea on microsomal oxidation of alcohols and associated microsomal functions. 42 8

The report by Schacter et al. (J Biol Chem 247: 3601, 1972) that an antibody to NADPH-cytochrome c oxidoreductase inhibited NADPH-cytochrome c reductase and heme oxygenase activities in rat and pig liver and spleen microsomes demonstrated the role of this flavoprotein in microsomal heme oxygenation. Recent studies from other laboratories (Yoshida et al., J Biochem 75, 1187: 1974 and Bissell et al., Fed Proc 33: 1246, 1974) have strongly suggested that cytochrome P-450 is not involved in heme oxygenation. The availability of a homogeneous preparation of NADPH-cytochrome c reductase prompted us to test heme oxygenase activity in a system devoid of hemoprotein contamination. NADPH-cytochrome c reductase catalyzed biliverdin formation at a rate of 8.26 +/- 0.5 SEM nmole min-1mg-1 in the absence of biliverdin reductase. The rate of bilirubin formation in the presence of biliverdin reductase was less than 10% of the rate of biliverdin formation, suggesting that mixture of biliverdin isomers may be produced. Biliverdin production was potently (70--80%) inhibited by catalase, but was unaffected by superoxide dismutase. Epinephrine also inhibited heme oxygenation, presumably by utilizing O2. required for the formation of H2O2 by the reductase. By extrapolation, the NADPH oxidase activity due to NADPH-cytochrome c reductase can account for heme degradation occurring in microsomes. However, the specificity of ring scission at the IXalpha position must be due to another microsomal protein, perhaps the heme oxygenase of Yoshida et al., and not cytochrome P-450.
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PMID:The catalysis of heme degradation by purified NADPH-cytochrome C reductase in the absence of other microsomal proteins. 82 31

Insulin caused a transient increase in H2O2 accumulation in human fat cell suspensions that was observed only in the presence of an inhibitor of catalase and heme-containing peroxidases, such as azide, and reached peak levels of 30 microM within 5 min. The cells contained a plasma membrane-bound NADPH oxidase, producing 1 mol H2O2/mol of NADPH oxidation, that was activated on exposure of intact cells to insulin at contrations that are physiologically relevant (0.1-10 nM). The hormone effect was rapid and was due to a selective increase in substrate affinity. The enzyme was magnesium dependent, required a flavine nucleotide for optimal activity, and was most active at pH 5.0-6.5. In contrast to all other hormone- or cytokine-sensitive NADPH oxidases that have been characterized in sufficient detail, the human fat cell oxidase retained its hormone responsiveness after cell disruption, and only Mn2+, but no ATP, was required for a ligand-induced activation in crude plasma membranes. The results demonstrate that insulin utilizes tyrosine kinase-independent pathways for receptor signaling and strongly support the view that H2O2 contributes to the intracellular propagation of the insulin signal.
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PMID:Human fat cells possess a plasma membrane-bound H2O2-generating system that is activated by insulin via a mechanism bypassing the receptor kinase. 131 14

Intraperitoneal administration of tuftsin-M [Thr-Lys-Pro-Arg-NH-(CH2)2-NH-CO-C15H31] to Balb/C mice has been shown to induce a respiratory burst in the peritoneal exudate cells. The macrophages exhibited enhanced levels of O2-, H2O2, NADPH oxidase and myeloperoxidase, but the activities of superoxide dismutase, catalase and glutathione peroxidase remained virtually unchanged. The magnitude of the oxidative burst depended directly on the dose of tuftsin-M; higher activity was observed at higher doses of the peptide. Tuftsin-M enhanced the generation of both O2- and H2O2 under in vitro conditions, as did phorbol myristate acetate. These results suggest that tuftsin-M could enhance non-specific defence against infections by activating the macrophages.
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PMID:Respiratory burst in peritoneal exudate cells in response to a modified tuftsin. 133 Jun 71

Primary cultures of rat liver Kupffer cells generated large amounts of superoxide anion radical (O2-.) when subjected to reoxygenation after a hypoxic period of at least 2 h. O2-. formation reached its maximum rate of approximately 25 nmol/10(6) cells within 1 h after reoxygenation. Two to four hours after reoxygenation, the number of injured cells began to increase and after 10 h approximately 60% of the cells were dead. During the period of O2-. release no significant difference in cell viability was observed between reoxygenated and hypoxically incubated cells, indicating a distinct time lag between O2-. release and onset of cell damage. Addition of diphenyliodonium, a specific inhibitor of the neutrophilic NADPH oxidase, to the Kupffer cells just before reoxygenation diminished both O2-. formation and cell injury up to 70%. Reoxygenation injury was completely prevented when superoxide dismutase and catalase were added immediately before reoxygenation. The results indicate that Kupffer cells subjected to hypoxia-reoxygenation generate a burst of reactive oxygen species and that this kind of "activation," probably by activating the NADPH oxidase, contributes to the self-destruction of the cells.
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PMID:O2-. release by activated Kupffer cells upon hypoxia-reoxygenation. 165 73

Rats were maintained on 20% and 4% protein diets for 3 weeks. The functional properties of thioglycollate (TG) elicited macrophages from these groups were compared with the non elicited resident cells from the protein fed group. Elicitation of macrophages in response to TG was low in the protein deficient group. These cells also exhibited low adherence in overnight cultures compared to those isolated from the protein fed group; however their viability and total protein content remained unaltered. Normal resident and TG elicited cells from 4% protein fed group exhibited an initial lag period in H2O2 production in response to zymosan stimulation. The lag period could be correlated to the high endogeneous catalase activity in these cells. Incubation with zymosan resulted in rapid decline in catalase levels, facilitating evolution of H2O2. On prolonged incubation, the elicited cells from the protein fasted rats evolved about 87% H2O2 compared to the protein fed samples. In the absence of zymosan all the samples possessed comparable NADPH oxidase activity. Zymosan induced activation of this enzyme was higher in TG cells from the protein fed groups, compared to the protein fasted and the resident samples. The cellular enzyme activity, however was not altered in the TG cells of both the groups though it declined rapidly in the corresponding resident cells. Significant reduction (congruent to 50%) in both serum iron and transferrin in the low protein fed samples did not correspondingly affect the oxidative burst process. However the engulfment of yeast cells was greatly impaired due to protein restriction. Adherence and phagocytic properties of macrophages are regulated by the activity of their membrane constituents.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of protein restriction on functional properties of rat peritoneal macrophages. 191 46

To determine the role of oxygen radicals in the killing of Mycobacterium tuberculosis by neutrophils, the effects of free-radical inhibitors and enzymes, catalase, superoxide dismutase, taurine, deferoxamine, and histidine were evaluated. Changes in the viability of M. tuberculosis were determined by agar plate colony counts and a radiometric assay. No impairment in killing was seen with any of the inhibitors or enzymes. Patients with chronic granulomatous disease (CGD) have a defect in the NADPH oxidase pathway, causing their neutrophils to be unable to generate oxygen radicals. If these radicals are involved in killing, then CGD neutrophils should be less effective killers of M. tuberculosis than normal neutrophils. There was no evidence by either measure of M. tuberculosis viability that CGD neutrophils were less bactericidal than normal neutrophils. Killing by normal neutrophils was also effective in the absence of serum. These results lead to the conclusion that the mechanism by which M. tuberculosis is killed by neutrophils is independent of the oxygen metabolic burst.
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PMID:Killing of Mycobacterium tuberculosis by neutrophils: a nonoxidative process. 190 38

The Ca++ ionophore A23187 and phorbol 12-myristate 13-acetate (PMA) caused dose-dependent inhibition of phospholipid (PL) methylation in unfractionated mononuclear cells (MNC), monocytes, and lymphocytes as measured by incorporation of 3H-methyl-groups from [3H-methyl]-L-methionine into phosphatidylcholine (PC), dimethyl phosphatidylethanolamine (PE), and monomethyl PE. This inhibitory effect did not correlate with monocyte superoxide release and was unaltered by the presence of either catalase and superoxide dismutase or the NADPH oxidase inhibitor, diphenylene iodonium (DPI), indicating that oxyradical-mediated oxidation of methionine was not the major cause of inhibition of PL methylation. Furthermore L-adrenaline, which elevates cAMP and does not stimulate superoxide release, also inhibited PL methylation. Inhibition by PMA was not due to reduction in intracellular levels of methionine or S-adenosyl methionine. A23187 caused reduction of S-adenosyl methionine levels only at 1 microM, and had no effect at lower concentrations. Inhibition of PL methylation was shown not to be due to phospholipase A2-dependent hydrolysis of newly methylated PL. Attempts to reverse the inhibitory effect of either A23187 or PMA with the putative protein kinase inhibitors W-7 and H-7 were inconclusive. The mechanism of inhibition of PL methylation by A23187 and PMA remains unclear, but does not appear to be due to oxidation of methionine or hydrolysis of newly methylated PL.
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PMID:Phorbol 12-myristate 13-acetate, A23187 and L-adrenaline inhibit phospholipid methylation in human monocytes and lymphocytes. Inhibition is independent of oxyradical production and phospholipid hydrolysis. 217 46

Neutrophils stimulated with formyl-methionyl-leucyl-phenylalanine (fMLP) or leukotriene B4 (LTB4) generated kinetically distinctive luminol augmented chemiluminescence (LCL). Inhibitors of .O2- [superoxide-dismutase (SOD) or tiron], H2O2 (catalase), myeloperoxidase, MPO, (NaN3), HOCl (taurine) and .OH (mannitol) hampered LCL dose-dependently with similar characteristics for both stimuli. In cell free systems it was found that .O2- (generated in the xanthine/xanthine-oxidase reaction) or H2O2 produced LCL. Superoxide dismutase inhibited .O2- -induced LCL dose dependently. The MPO + H2O2 system, which generated more pronounced LCL than either component alone, was inhibited by catalase and taurine but not by SOD. When neutrophils, treated with luminol, but where extracellular luminol had been removed, were stimulated with fMLP or LTB4, they produced less than 2% of the LCL where luminol was present in the medium. When neutrophil LCL and superoxide formation by the cytochrome C method were assessed in parallel experiments, in all instances the peak LCL response coincided with the linear phase in that response. Thus, LCL, induced by LTB4 and the corresponding fMLP peak, are extracellular events with similar chemical backgrounds, closely related to generation of reactive oxygen species. Consequently, the kinetical differences in LCL between fMLP and LTB4 suggest that LTB4, by yet unknown mechanisms, activates the NADPH oxidase more rapidly than fMLP.
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PMID:Mechanisms for luminol-augmented chemiluminescence from neutrophils induced by leukotriene B4 and N-formyl-methionyl-leucyl-phenylalanine. 254 May


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