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At least 109 records · Page 6Linked to original sources
PubMed1976

Plant microbody proteins. II. Purification and characterization of the major protein component (SP-63) of peroxisome membranes.

The major component of membranes of microbodies from green leaves of Lens culinaris is a protein of a subunit molecular weight of 63 000. This protein, referred to as SP-63, seems to be unique to microbodies and could not be detected when plastids or mitochondria were analyzed. It is probably a structural protein and is thus not solubilized by cholate, Triton X-100, chloroform/methanol, or 0.2M KCl. Solubilization from purified membranes was achieved with guanidinium chloride or sodium dodecylsulphate. The protein was separated from minor contaminating components by chromatography on Sepharose 4B or Sephadex G-150 employing 0.1% sodium dodecylsulphate or 4M urea as eluent. It was shown to be homogeneous upon sodium dodecylsulphate gel electrophoresis and did not give a positive glycoprotein stain.

Guanidines↗
PubMed1990

Transition form of microbodies. Overlapping of two sets of marker proteins during the rearrangement of glyoxysomes into leaf peroxisomes.

Several forms of microbodies have been characterized on the basis of their biochemical functions. We have investigated cucumber cotyledons which house two different microbody forms during their development. In these cells, a shift from organelles with the enzymes of beta-oxidation and glyoxylate cycle to peroxisomes with the enzymes of the photosynthetic C2-cycle can be induced by light. The transition state and the time course of changes was studied at different levels of gene expression during the first 2 days of illumination, by quantifying the rate of de novo protein synthesis in cotyledons and by measuring the mRNA activities in vitro. Synthesis and turnover of particular proteins were determined during the transition stage by immunoprecipitation of malate synthase, isocitrate lyase, catalase, multifunctional protein, and thiolase, and quantified by fluorography. From the mRNA activities and the rate of protein synthesis, gene expression for enzymes of the glyoxylate cycle and beta-oxidation started to decrease 24-36 h after onset of continuous light. At that time the rate of synthesis of glycolate oxidase, a leaf peroxisomal marker, is already maximal. By pulse-chase experiments 0-48 h after the onset of light the speed and intensity of protein turnover were measured. Rates of proteolytic degradation of individual enzymes indicated that the different enzymes were not lost simultaneously or all at once. This excludes a destruction of the whole organelle by the lytic compartment.

Gene Expression↗
PubMed1978

Isolation and biochemical properties of two types of microbody from Neurospora crassa cells.

Cells of the Neurospora crassa slime mutant grown in sucrose medium exhibited low activities of glyoxysomal marker enzymes isocitrate lyase (ICL), malate synthetase (MS), and malate dehydrogenase. Transfer of the cells to a medium containing acetate as sole carbon source ("acetate medium") induced a strong increase in the activities of these enzymes in both the soluble and the crude particulate cell fraction. Soluble isocitrate lyase activity increased rapidly after a lag phase of about 45 minutes. Addition of 0.1 mM cycloheximide to the acetate medium 3 hours after transfer of the cells halted the rise of isocitrate lyase activity in either cell fraction, but the inhibition of the incorporation of ICL activity into the particulate cell fraction was delayed by 1 hour. Addition of 20 g/l glucose resulted in the immediate decrease of both soluble and particulate ICL activities. Transfer to acetate medium induced no change in the activities of other microbody marker enzymes such as catalase, uricase or D-amino acid oxidase. Resolution of crude homogenates of "slime" cells by sucrose density gradient centrifugation yielded two major protein bands: A mitochondrial band at a density of 1.180 kg/l showing maximum activites of fumarase, isocitrate dehydrogenase and cytochrome c oxidase, and a microbody-rich band which obviously consisted of two types of organelles with different biochemical properties. Maximum activities of ICL and MS sedimented at a density of 1.21 kg/l while the peaks of particulate uricase and catalase activities were recovered at 1.24 kg/l.

Acetates↗
PubMed1993

The hydrogenosomal enzyme hydrogenase from the anaerobic fungus Neocallimastix sp. L2 is recognized by antibodies, directed against the C-terminal microbody protein targeting signal SKL.

The question was addressed whether antibodies directed against the general microbody C-terminal protein targeting signal SKL recognized hydrogenosomal proteins from Neocallimastix sp. L2. Immunofluorescence, immunocytochemistry and Western blotting experiments using these antibodies indicated the presence of hydrogenosomal proteins containing SKL-COOH. One of these proteins, the hydrogenase, was purified to homogeneity. It has a native molecular mass of 87 kDa and consists of two subunits of approximately 30 and 60 kDa, both cross-reacting with anti-SKL antibodies. Its activity could be inhibited by CO, NO2-, and acetylene, suggesting a (Ni-Fe-Se) hydrogenase. Immunocytochemistry using polyclonal antibodies raised against the hydrogenase revealed the location of this protein in the hydrogenosomal matrix. The results described in this paper suggest that hydrogenosomes from Neocallimastix sp. L2 are related to microbodies from aerobic eukaryotes and support the idea of a common evolutionary origin for these organelles.

Amino Acid Sequence↗
PubMed1976

Microbodies from spirogyra: organelles of a filamentous alga similar to leaf peroxisomes.

Organelles from Spirogyra cells were separated on a linear sucrose gradient. After centrifugation, most of the protein was found in the top fraction. Two minor protein peaks at density (g/cm(3)) 1.17 and 1.21 were due to chloroplast particles and mitochondria, respectively. Although there was an extremely low concentration of protein at density 1.25 g/cm(3), a major part of the activity of glycolate oxidase was found in this region. The enzyme was able to transfer electrons to O(2) and only lost 12% of its activity in the presence of 1 mm cyanide. As documented by electron micrographs, microbodies moved to density 1.25 g/cm(3) during centrifugation. This observation, as well as the fact that high activities of hydroxypyruvate reductase and catalase were also found at the same density, suggest that the microbodies from Spirogyra are similar to those in green leaves of higher plants.

Journal Article↗
PubMed1977

Polymorphism of Microbody Malate Dehydrogenase in Opuntia basilaris.

Electrophoretic survey of malate dehydrogenase (EC 1.1.1.37) in Opuntia basilaris showed intraspecific polymorphism. Further experiments with microbody malate dehydrogenase-specific antiserum suggest that the polymorphism occurs in microbody malate dehydrogenase independent of the soluble and mitochondrial forms. The pattern of polymorphism is one expected from a two-allele Mendelian system.

Journal Article↗
PubMed1980

Synthesis of Isocitrate Lyase in Sunflower Cotyledons during the Transition in Cotyledonary Microbody Function.

Density-labeling with 10 millimolar K(15)NO(3)/70% (2)H(2)O has been used to investigate isocitrate lyase synthesis during greening of sunflower (Helianthus annuus L.) cotyledons when the glyoxysomal enzyme activities sharply decline and the transition in cotyledonary microbody function occurs. A density shift of 0.0054 (kilograms per liter) was obtained for the profile of isocitrate lyase activity in the CsCl gradient with respect to the (1)H(2)O control. Quantitative evaluation of the density-labeling data indicates that about 50% of the isocitrate lyase activity present towards the end of the transition stage in microbody function is due to enzyme molecules newly synthesized during this stage.

Journal Article↗
PubMed1965

Alpha-hydroxy acid oxidase: localization in renal microbodies.

Differential and density equilibrium centrifugation have established the presence of alpha-hydroxy acid oxidase in microbodies of the kidney of the rat. The enzyme has been demonstrated in cells of the distal convoluted tubule by a microscopic cytochemical method. This enzyme, like certain others in microbodies, produces hydrogen peroxide.

Acid Phosphatase↗
PubMed1997

Trypanosoma brucei: identification of an internal region of phosphoglycerate kinase required for targeting to glycosomal microbodies.

Among the microbodies found in eukaryotes are the glycosomes of Trypanosoma brucei, thought to be closely related to peroxisomes. Two types of targeting signals for glycosomes have been identified thus far: type 1 at the C-terminus and type 2 at the N-terminus. In this report, we use an epitope-tagging system to characterize the targeting signal found on the minor glycosomal isozyme of phosphoglycerate kinase, 56PGK. No type 1 or 2 signal was found; rather, the topogenic information was found to be internal. Chimeric molecules formed with the cytoplasmic phosphoglycerate kinase isozyme indicate that a region between amino acids 24 and 91 of 56PGK is essential for glycosomal targeting. No homology was found between this region and peroxisomal proteins containing internal targeting signals.

Amino Acid Sequence↗
PubMed1996

Pumpkin hydroxypyruvate reductases with and without a putative C-terminal signal for targeting to microbodies may be produced by alternative splicing.

Two full-length cDNAs encoding hydroxypyruvate reductase were isolated from a cDNA library constructed with poly(A)+ RNA from pumpkin green cotyledons. One of the cDNAs, designated HPR1, encodes a polypeptide of 386 amino acids, while the other cDNA, HPR2 encodes a polypeptide of 381 amino acids. Although the nucleotide and deduced amino acid sequences of these cDNAs are almost identical, the deduced HPR1 protein contains Ser-Lys-Leu at its carboxy-terminal end, which is known as a microbody-targeting signal, while the deduced HPR2 protein does not. Analysis of genomic DNA strongly suggests that HPR1 and HPR2 are produced by alternative splicing.

Alcohol Oxidoreductases↗
PubMed1977

Peroxisomes (microbodies) in the myocardium of rodents and primates. A comparative Ultrastructural cytochemical study.

The occurrence of peroxisomes (microbodies), their cytochemical characteristics and their ultrastructural relationship to the neighboring organelles were investigated in the ventricular myocardium of four rodent (rat, rabbit, gerbil, and guinea pig) and two primate (Macaca java and Tupaya) species. The hearts were fixed by vascular perfusion with glutaraldehyde and incubated in alkaline diaminobenzidine media for visualization of catalase. The electron-dense reaction product of catalase was found in the myocardium of all examined species and was localized in 0.2--0.5 mum oval particles, surrounded by a single limiting membrane and located usually at the junction of I and A bands. The peroxisomes in the hearts of gerbil and Macaca java were especially long and tortuous. A close spatial association was found between the myocardial peroxisomes and mitochondria, lipid droplets, and the membranes of sarcoplasmic reticulum, especially the so-called junctional sarcoplasmic reticulum. These observations demonstrate the consistent occurrence of peroxisomes in the heart of various mammalian species and suggest that peroxisomes have important metabolic and physiological functions in myocardium.

Animals↗
PubMed1989

Occurrence and metabolic significance of microbodies in trophic hyphae of the nematophagous fungus Arthrobotrys oligospora.

This paper describes the results of an ultrastructural study on the subcellular events occurring in nematode-infecting (trophic) hyphae of the nematophagous fungus Arthrobotrys oligospora. In early stages of the infection process (30 min-4 h), the infection bulb and developing trophic hyphae are characterized by a highly proliferated endoplasmic reticulum (ER). Its membranes often appeared vesiculated and occur in close association with the cell membrane of the cells. Upon further invasion of the nematode, lipid droplets developed in the trophic hyphae; these droplets were first observed 4-5 h after the infection but were abundantly present after 24-36 h. Along with the formation of lipid droplets proliferation of microbodies was observed. These organeles were characterized by the presence of catalase and thiolase and were frequently observed in close association with the lipid droplets. Later on the lipid droplets disappeared. During this period new vegetative mycelium developed from the trap that had originally captured the nematode. Our results suggest that part of the nutrients released from the nematode are first converted into lipids by the fungus which in turn are degraded via the beta-oxidation pathway and further metabolized to support growth of new vegetative hyphae.

Animals↗
PubMed1975

Microbodies in methanol-assimilating yeasts.

Cells of 3 yeast species capable of assimilating methanol have been examined by electron microscopy. When grown on methanol as the sole source of carbon and energy they contained many microbodies. Cells grown on glucose or ethanol either did not contain such bodies at all, or only to a limited extent.

Ascomycota↗
PubMed1975

Histochemical and biochemical evidence for the presence of microbodies in phytophthora palmivora.

Using the diaminobenzidine (DAB) reaction catalase activity could be demonstrated histochemically in cytoplasmic structures of Phytophthora palmivora bearing general ultrastructural features of microbodies. These socalled U-bodies sediment together with the catalase activity in Ficoll-Sorbitol-Sucrose gradients following prior purification by differential centrifugation.

3,3'-Diaminobenzidine↗
PubMed1980

Peroxisomes (microbodies) in human glial tumors. a cytochemical ultrastructural study.

Morphologically and cytochemically defined peroxisomes (microbodies) were demonstrated in a series of 11 human glial tumors. The cytochemical methods used were diaminobenzidine method for catalase and a tetrazolium salt-phenozine methosulfate method for D-amino-acid oxidase. Ultrastructurally, the peroxisomes were found as single membrane limited organelles with a granular matrix. Marginal plates as well as continuities with the smooth endoplasmic reticulum could be demonstrated. Peroxisomes were found most abundantly in subependymal giant cell astrocytomas, to a lesser number in astrocytomas and least abundantly in glioblastomas.

Adolescent↗
PubMed1984

Localization of the initial steps in alkoxyphospholipid biosynthesis in glycosomes (microbodies) of Trypanosoma brucei.

Cell fractionation of Trypanosoma brucei cultured procyclic stages showed that the key enzyme of glycerol-ether lipid synthesis, dihydroxyacetone-phosphate acyltransferase (EC 2.3.1.42) was exclusively associated with the microbody fraction. These organelles contained in addition 1-acyl glycerol-3-phosphate: NADP+ oxidoreductase (EC 1.1.1.101) and acyl-CoA reductase and were capable of utilizing DHAP, but not G-3-P, as substrate for lysophosphatidic acid formation. It is concluded that in T. brucei the glycosomes are the exclusive site of the synthesis of precursors for glycerol-ether lipid synthesis and that they contain the entire pathway to form alkoxylipids from glycerol and acyl-CoA.

Acylation↗
PubMed1988

Demonstration of glycosomes (microbodies) in the Bodonid flagellate Trypanoplasma borelli (Protozoa, Kinetoplastida).

Homogenates of Trypanoplasma borelli were subjected to subcellular fractionation by sequential differential and isopycnic centrifugation in sucrose. Glycerol-3-phosphate dehydrogenase and the glycolytic enzymes, glucosephosphate isomerase and triosephosphate isomerase, as well as the peroxisomal marker enzyme catalase were mainly, or in part, associated with sedimentable particles that had a buoyant density in sucrose of 1.22 g cm-3. Moreover, triosephosphate isomerase exhibited latency, both in total homogenates and in the particulate fraction. Electron microscopy of thin sections of T. borelli revealed the presence of microbodies that gave a positive reaction for catalase. Pyruvate kinase behaved as a typical soluble enzyme. It was stimulated by micromolar concentrations of fructose 2,6-bisphosphate and this stimulation was counteracted by inorganic phosphate in the millimolar range. The enzymes involved in the synthesis and degradation of fructose 2,6-bisphosphate, 6-phosphofructo-2-kinase and fructose-2,6-bisphosphatase, were both present in T. borelli and behaved as soluble enzymes. We conclude that in T. borelli the glycolytic pathway is compartmentalized in a way similar to that found in another Kinetoplastid family, the Trypanosomatidae, where seven glycolytic enzymes and two enzymes of glycerol metabolism are associated with glycosomes. Apparently the presence of glycosomes is a characteristic of all Kinetoplastida.

Animals↗