Showing papers on "Catalase published in 1972"

Hepatic Microsomal Ethanol Oxidation

Abstract: Microsomes from rat liver form hydrogen peroxide in the presence of an NADPH-generating system in proportion to protein concentrations as determined by three independent methods: ferrithiocyanate, cytochrome c peroxidase, and scopoletin fluorescence. Maximal rates observed were about 15 μmol H2O2/g microsomal protein per minute. The oxygen concentration for half-maximal rates was 50 μM. It is suggested that NADPH-dependent hydrogen peroxide formation in microsomes is mainly due to NADPH oxidase; however, partial inhibition by carbon monoxide suggests that about one third arises from the autoxidation of cytochrome P-450. Similarities exist between microsomal acetaldehyde production from ethanol (i.e. the microsomal ethanol-oxidizing system of Lieber and DeCarli [4]) and hydrogen peroxide formation: viz. requirement for NADPH and oxygen, identical oxygen concentrations for halfmaximal rates, and sensitivity to carbon monoxide. Microsomal acetaldehyde production in the presence of either an NADPH- or an H2O2-generating system exhibits identical characteristics as follows: (a) ethanol concentration for half-maximal rates (i.e. 12 mM); (b) dependency of maximal rates on rates of hydrogen peroxide formation; (c) competitive inhibition by peroxidatic substrates for catalase, e.g. formate (half-maximal effect: 150 μM); (d) inhibition by catalase inhibitors, e.g. azide (half-maximal effect: 50 μM), with identical azide insensitive rates; (e) diminished acetaldehyde production in microsomes from rats pretreated with aminotriazole or pyrazole with identical residual rates. Moreover, NADPH-dependent acetaldehyde production is suppressed in the presence of an active H2O2-utilizing system. Thus, it is concluded that the NADPH-dependent microsomal ethanol-oxidizing system of Lieber and DeCarli [4] is due to a hydrogen peroxide formation from NADPH and a subsequent peroxidation of ethanol by contaminating catalase. The data indicate that the existence of a unique system in addition to the peroxidatic reaction of catalase as postulated recently [4] is highly doubtful.

Further studies on the generation of hydrogen peroxide by 6-hydroxydopamine. Potentiation by ascorbic acid.

Abstract: We studied the inhibitory action of various compounds, including hydrogen peroxide, on the uptake of [3H]dopamine by rat brain slices. Dialuric acid, 6-hydroxydopamine, and 5-hydroxydopamine consumed oxygen and generated hydrogen peroxide in solution as a result of aerobic oxidation, as measured with an oxygen electrode. The regeneration by catalase of half the oxygen consumed by 6-hydroxydopamine confirmed that oxygen consumption was equal to H202 production. The rate of oxygen uptake (H202 production by dialuric acid or 6-hydroxydopamine was augmented by the addition of ascorbic acid. In addition, alloxan, which is the oxidized form of dialuric acid, consumed oxygen when ascorbate was added. The mechanism for this can be envisaged as reduction of the oxidized compounds by ascorbate, followed by reoxidation to form more H202, with continuous recycling. Concomitant with increased production of H202, there was increased inhibition of [3H]dopamine uptake. Ascorbate by itself did not inhibit the uptake of [3H]dopamine and did not produce measurable quantities of H202. 6-Hydroxydopamine, a compound that causes nerve terminal degeneration in vivo, was compared with 5-hydroxydopamine, which does not. As both compounds are structural analogues of dopamine, they can inhibit the uptake of [3H]dopamine into brain slices by competing for the uptake mechanisms. Additionally, both may inhibit uptake irreversibly by generating H2O2, which causes oxidative damage. 6-Hydroxydopamine produced H202 at about 12 times the rate yielded by 5-hydroxydopamine. Ascorbate potentiated H2O2 production by 6-hydroxydopamine but suppressed that from 5-hydroxydopamine. These findings are consistent with an important role for H2O2 in the 6-hydroxydopamine-induced degeneration of nerve terminals and may explain why 5-hydroxydopamine does not produce degenerative changes.

Developmental studies on microbodies in wheat leaves : I. Conditions influencing enzyme development.

Abstract: Catalase, glycolate oxidase, and hydroxypyruvate reductase, enzymes which are located in the microbodies of leaves, show different developmental patterns in the shoots of wheat seedlings. Catalase and hydroxypyruvate reductase are already present in the shoots of ungerminated seeds. Glycolate oxidase appears later. All three enzymes develop in the dark, but glycolate oxidase and hydroxypyruvate reductase have only low activities. On exposure of the seedlings to continuous white light (14.8 x 10(3) ergs cm(-2) sec(-1)), the activity of catalase is doubled, and glycolate oxidase and hydroxypyruvate reductase activities increase by 4- to 7-fold. Under a higher light intensity, the activities of all three enzymes are considerably further increased. The activities of other enzymes (cytochrome oxidase, fumarase, glucose-6-phosphate dehydrogenase) are unchanged or only slightly influenced by light. After transfer of etiolated seedlings to white light, the induced increase of total catalase activity shows a much longer lag-phase than that of glycolate oxidase and hydroxypyruvate reductase. It is concluded that the light-induced increases of the microbody enzymes are due to enzyme synthesis. The light effect on the microbody enzymes is independent of chlorophyll formation or the concomitant development of functional chloroplasts. Short repeated light exposures which do not lead to greening are very effective. High activities of glycolate oxidase and hydroxypyruvate reductase develop in the presence of 3-amino-1,2,4-triazole which blocks chloroplast development. The effect of light is not exerted through induced glycolate formation and appears instead to be photomorphogenetic in character.In senescing leaves excised from the plants decreases in activity of glycolate oxidase, and hydroxypyruvate reductase follow with some delay the decrease in chlorophyll content. The activity of catalase, however, is maintained at high levels, especially when the detached shoots are kept in light.

Oxidation of Methanol, Formaldehyde and Formate by a Candida Species

Abstract: 1. The oxidation of methanol to carbon dioxide by Candida N–16 grown on methanol was investigated. The presence of enzymes which catalyze the following reaction was found in the cell-free extract of the yeast employed; CH3OH→HCHO→HCOOH→CO2. 2. Methanol was oxidized to formaldehyde by an alcohol oxidase. The reaction was as follows; CH3OH+O2→HCHO+H2O2. The alcohol oxidase was crystallized after purification by ammonium sulfate-precipitation and column chromatography using DEAE-Sephadex A-50. A prosthetic group of the enzyme was proved to be FAD. The enzyme possessed a broad specificity for alcohols such as methanol, ethanol, n-propanol, n-butanol and n-amylalcohol. The enzyme was inducibly formed only by the addition of methanol. 3. The oxidation of formaldehyde to formate was catalyzed by a NAD-linked dehydrogenase dependent on GSH. 4. Formate was oxidized by a NAD-linked dehydrogenase. 5. Catalase was also found in the extract, and methanol was chemically oxidized by the reaction of catalase and hydrogen...

Method of puffing tobacco and reducing nicotine content thereof

Abstract: A method is provided for treating tobacco to increase the volume of the tobacco and reduce the nicotine and tar content of the tobacco. According to the method of the invention, tobacco is treated with a given amount of catalase and an aqueous solution containing a given amount of hydrogen peroxide, with the hydrogen peroxide and catalase being applied either simultaneously or first with the hydrogen peroxide and then with the catalase. The treated tobacco thus produced is especially useful in the manufacture of cigarettes and the like.

Catalase activity and red cell metabolism.

Abstract: Catalase (H2O2:O2 oxidoreductase) is present in high concentrations in several tissues of the human body, among them the liver and the erythrocyte. Erythrocyte catalase is thought to mediate the detoxification of H2O2 in the following fashion (Deisseroth and Dounce, 1970):

Increase in hepatic catalase and glycerol phosphate dehydrogenase activities on administration of clofibrate and clofenapate to the rat.

Abstract: 1. Clofenapate (methyl 2-[4-(p-chlorophenyl)phenoxy]-2-methylpropionate) fed to the rat in the diet increased the content of mitochondrial protein in the liver by 50–60%. In this respect it resembled the related compound clofibrate (ethyl α-p-chlorophenoxyisobutyrate), which is widely used as an antihypercholesterolaemic drug. 2. Both compounds when fed to the rat enhanced the activity of α-glycerol phosphate dehydrogenase in the liver mitochondria manyfold, but were without effect on the enzyme in the soluble fraction. 3. On the other hand, the catalase activity in the supernatant fraction increased twofold after administration of the drugs. The mitochondrial catalase activity showed a consistent decrease. 4. It was unlikely that under the influence of the drug the increase in catalase activity took place in the mitochondrial particles and was leached into the cytosol during isolation. 5. The increase in catalase activity in the cytosol under the influence of the drug is best explained on the assumption that peroxisomes which contain this enzyme, and which are known to increase on administration of the drug, were broken during the process of cellular fractionation and released the enzyme into the cytosol. 6. All the above effects shown by both drugs were fully reversed when drugs were withdrawn from the diet. 7. Clofenapate was effective in bringing about the above changes when administered to the animal at one-hundredth the concentration of clofibrate.

Liver and blood cell catalase activity of tumor-bearing mice.

Abstract: Summary Liver and blood cell catalase activity in mice with and without tumors of various sizes and origins was measured. Animals bearing tumors ⩾1.5 cm in size showed depression of leukocyte and/or liver catalase activity when compared with tumor-free animals, but this effect was not significant in mice with smaller tumors. No depression of erythrocyte catalase activity was observed.

Formation of compound I by the reaction of catalase with peroxoacetic acid.

Abstract: 1. The formation of Compound I by the reactions of bacterial and ox liver catalases with peroxoacetic acid was examined. In both cases the process occurs almost entirely by reaction of catalase with un-ionized peroxoacetic acid molecules. The result suggests an important role for the bound peroxidic proton in the enzyme–substrate interaction. 2. The peroxidatic properties of the Compounds I formed when peroxoacetic acid was used were examined by studying the oxidations of ethanol and formate; the results closely resemble those previously reported when H2O2 and alkyl hydroperoxides were used. 3. Compound I formed with bacterial catalase and peroxoacetic acid is remarkably stable in the absence of added donor and the preparation has considerable potential for detailed studies of the nature of this intermediate.

Inactivation of immobilized catalase by hydrogen peroxide in continuous reactors

Abstract: It is shown theoretically that in continuous reactions the rate of catalase inactivation by hydrogen peroxide depends on the type of reactor and the order of the chemical reaction.