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Query: UNIPROT:P04040 (Catalase)
 3,577 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Malate synthase from baker's yeast, a trimeric sulfhydryl enzyme with one essential sulfhydryl group per subunit, was inactivated by 2 kGy X-irradiation in air-saturated aqueous solution (enzyme concentration: 0.5 mg/ml). The radiation induced changes of enzymic activity were registered at about 0, 30, 60 h after irradiation. To elucidate the role of OH., O-.2, and H2O2 in the X-ray inactivation of the enzyme, experiments were performed in the absence or presence of different concentrations of specific additives (formate, superoxide dismutase, catalase). These additives were added to malate synthase solutions before or after X-irradiation. Moreover, repairs of inactivated malate synthase were initiated at about 0 or 30 h after irradiation by means of the sulfhydryl agent dithiothreitol. Experiments yielded the following results: Irradiation of malate synthase in the absence of additives inactivated the enzyme immediately to a residual activity Ar = 3% (corresponding to a D37 = 0.6 kGy), and led to further slow inactivation in the post-irradiation phase. Repairs, initiated at different times after irradiation, restored enzymic activity considerably. The repair initiated at t = 0 led to Ar = 21%; repairs started later on resulted in somewhat lower activities. The decay of repairability, however, was found to progress more slowly than post-irradiation inactivation itself. After completion of repair the activities of repaired samples did not decrease significantly. The presence of specific additives during irradiation caused significant protective effects against primary inactivation. The protection by formate was very pronounced (e.g., Ar = 72% and D37 = 6 kGy for 100 mM formate). The presence of catalytic amounts of superoxide dismutase and/or catalase exhibited only minor effects, depending on the presence and concentration of formate. Both the presence of specific additives during irradiation and the addition of additives after irradiation may alter the post-irradiation inactivation. Catalase turned out to be the most potent inhibitor of post-irradiation inactivation; superoxide dismutase showed an ambivalent behaviour, it accelerated or impeded post-irradiation inactivation; formate, when added after irradiation, exhibited a moderate protective effect. The presence of specific additives, added before and/or after irradiation, influenced the repair behaviour to some extent. The highest activity achieved by repair amounted to about 90% of the activity of the corresponding unirradiated sample. The percentual gain of activity was found to be the greater the lower the residual activity of the enzyme was before initiation of repair.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Post-irradiation inactivation, protection, and repair of the sulfhydryl enzyme malate synthase. Effects of formate, superoxide dismutase, catalase, and dithiothreitol. 401 52

A purification scheme is described for the glyoxylate cycle enzyme malate synthase from maize scutella. With our procedure, large amounts of extremely pure enzyme can easily be prepared. Purification involves a heat denaturation step, followed by ammonium sulfate precipitation, and chromatography on DEAE-cellulose and Blue Dextran-Sepharose. Catalase and malate dehydrogenase, which are the most persistent contaminants, are completely removed by this procedure. Maize malate synthase is an octameric protein with a subunit molecular weight of 64 kDa. Purity of the enzyme preparation was demonstrated by SDS-polyacrylamide gel electrophoresis and by isoelectric focusing (pI = 5.0). Pure malate synthase can be stored without appreciable loss of activity at -70 degrees C in 200 mM Hepes buffer containing 6 mM MgCl2 and 2 mM 2-mercaptoethanol, pH 7.6. Maize malate synthase contains no covalently linked carbohydrate residues. The enzyme requires Mg2+ ions for activity. From circular dichroism measurements we estimate that the secondary structure of the enzyme consists of 30% alpha-helical and almost no (5%) beta-pleated sheet segments. A 45-kDa polypeptide, which contaminates malate synthase preparations if the purification starts from seedlings older than 2.5 days, is shown to be a degradation product of malate synthase. Together with full-length chains, these 45-kDa polypeptides are able to take part in octameric oligomer formation.
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PMID:Purification of the glyoxylate cycle enzyme malate synthase from maize (Zea mays L.) and characterization of a proteolytic fragment. 828 48

Changes in the ultrastructural aspect of the glyoxysome fraction obtained from maize scutella by density gradient centrifugation were followed during the first 6 days of germination. During the first 2 days the fraction consists of very electron-dense bodies about 0.3 to 0.5 micron in size while at the 4th day it is formed by larger and less dense membrane-bound particles. Some intermediate form between the two types of organelles can be seen at the 3rd day. Between the 4th and the 6th days of germination the glyoxysomes are destroyed, and their enzymes are released into the cytosol. At the peak of their development (4th day) the glyoxysomes contain 75 to 80% of the total isocitratase and 65% of the total malate synthetase of the scutellum. These values drop to very low levels during the next 2 days. Catalase bound to glyoxysomes amounts to 30 to 35% of the total activity present in the scutellum at the 1st day of germination: this value decreases steadily during the following days.
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PMID:The development of glyoxysomes in maize scutellum: changes in morphology and enzyme compartmentation. 1665 12

The sequence of glyoxysomal enzyme development was investigated in cotyledons of cotton (Gossypium hirsutum L. cv. Deltapine 16) embryos from 16 to 70 days after anthesis (DAA). Catalase, malate dehydrogenase, and citrate condensing enzyme activities were barely detectable prior to 22 DAA, but showed dramatic increases from 22 to 50 DAA. Development of malate synthase activity, however, was delayed during this period, rising to peak activity from 45 to 50 DAA (just prior to desiccation) in the absence of any detectable isocitrate lyase activity. Substantial activities of all of these enzymes (except isocitrate lyase) persisted in the dry seeds. Isopycnic centrifugations on sucrose gradients demonstrated that the enzymes were compartmentalized within particles increasing in buoyant density with time of development (1.226 to 1.245 grams per cubic centimeter from 22 to 50 DAA). Of particular significance were the observations in 22-day embryos of smooth surfaced membrane dilations of rough endoplasmic reticulum having cytochemical catalase reactivity, and the demonstrations of catalase activities in microsomal fractions isolated throughout the 16- to 50-DAA period. Our data do not allow determination of the mechanism(s) for enzyme activation and/or addition to previously existing or newly formed microbodies, but do show that development and acquisition of enzyme activities within glyoxysomes occur sequentially and thus are not regulated in concert as previously thought.
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PMID:Control of Enzyme Activities in Cotton Cotyledons during Maturation and Germination: II. Glyoxysomal Enzyme Development in Embryos. 1666 Apr 55

The distribution of glyoxylate-cycle enzymes between microbodies and mitochondria was examined in ethanol-grown Aspergillus tamarii Kita. Particulate activities of catalase and the two glyoxylate by-pass enzymes, malate synthase and isocitrate lyase, were localized in the microbodies. The microbodies had a buoyant density of about 1.23 g cm(-3) after isopycnic centrifugation in linear sucrose gradients. Particulate activities of the other two glyoxycitrate synthase, together with that of succinate dehydrogenase were restricted to the mitochondria, which had a buoyant density of about 1.20 g cm(-3). Catalase also appeared to be localized in a second particle, perhaps the microbody inclusions or the Woronin bodies, having a buoyant density of about 1.26 g cm(-3).
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PMID:Distribution of glyoxylate-cycle enzymes between microbodies and mitochondria in Aspergillus tamarii. 2442 91

Microbodies were observed in the hyphal tips of all 14 fungi investigated. Their morphology varied among the fungi and their numbers were influenced by the growth medium. Microbodies were closely associated with mitochondria in one fungus and with the endoplasmic reticulum in several fungi. Catalase was not detected in microbodies with the diaminobenzidine cytochemical procedure even though catalase activity was present in extracts of these fungi. The activities of the glyoxylate-cycle enzymes isocitrate lyase and malate synthase were affected by the growth medium and were particulate in the two fungi studied by differential centrifugation. Microbodies are abundant, and they are ubiquitous among the fungi and in some cases they may contain glyoxylate-cycle enzymes.
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PMID:Microbodies and glyoxylate-cycle enzyme activities in filamentous fungi. 2443 28