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At least 127 records · Page 7Linked to original sources
PubMed1993

Characterization of a divergent glycosomal microbody phosphoglycerate kinase from Trypanosoma brucei.

There are 3 loci in the phosphoglycerate kinase (PGK) gene complex of Trypanosoma brucei. The PGK-A gene product, which we term 56PGK, is targeted to glycosomal microbodies and is highly homologous to the parasite's 2 known PGKs (one cytoplasmic and one glycosomal). However, 56PGK contains an 80 amino acid insertion as well as numerous substitutions compared to the other PGKs. The complementation and kinetic analyses described here demonstrate that 56PGK is an authentic phosphoglycerate kinase--the largest yet described. When expressed in Escherichia coli, 56PGK complements the pgk- phenotype. 56PGK was expressed as a fusion protein and purified to near homogeneity. The Michaelis constants are similar to those of other PGKs, being 0.12 and 2.4 mM for Mg-ATP and 3-phosphoglycerate, respectively. As with other T. brucei PGKs, ATP but not GTP or ITP can serve as a phosphate donor during catalysis. No evidence was obtained for phosphate transfer to atypical substrates. 56PGK shows sulfate inhibition at all concentrations tested, rather than the sulfate activation observed with yeast PGK.

Amino Acid Sequence↗
PubMed1992

Glycosome assembly in trypanosomes: variations in the acceptable degeneracy of a COOH-terminal microbody targeting signal.

Trypanosomes compartmentalize most of their glycolytic enzymes in a peroxisome-like microbody, the glycosome. The specificity of glycosomal targeting was examined by expression of chloramphenicol acetyltransferase fusion proteins in trypanosomes and monkey cells. Compartmentalization was assessed by cell fractionation, differential detergent permeabilization, and immunofluorescence. The targeting signal of trypanosome phosphoglycerate kinase resides in the COOH-terminal hexapeptide, NRWSSL; a basic amino acid is not required. The minimal targeting signal is, as for mammalian cells, a COOH-terminal tripeptide related to -SKL. However, the acceptable degeneracy of the signal for glycosomal targeting in trypanosomes is considerably greater than that for peroxisomal targeting in mammals, with particularly relaxed requirements in the penultimate position.

Amino Acid Sequence↗
PubMed1984

Purification, morphometric analysis, and characterization of the glycosomes (microbodies) of the protozoan hemoflagellate Trypanosoma brucei.

Trypanosoma brucei glycosomes (microbodies containing nine enzymes involved in glycolysis) have been purified to near homogeneity from bloodstream-form trypomastigotes for the purpose of morphologic and biochemical analysis. Differential centrifugation followed by two isopycnic centrifugations in an isotonic Percoll and in a sucrose gradient, respectively, resulted in 12- to 13-fold purified glycosomes with an overall yield of 31%. These glycosomes appeared to be highly pure and contained less than 1% mitochondrial contamination as judged by morphometric and biochemical analyses. In intact cells, glycosomes displayed a remarkably homogeneous size distribution centered on an average diameter of 0.27 micron with a standard deviation of 0.03 micron. The size distribution of isolated glycosomes differed only slightly from that measured in intact cells. One T. brucei cell contained on average 230 glycosomes, representing 4.3% of the total cell volume. The glycosomes were surrounded by a single membrane and contained as phospholipids only phosphatidyl choline and phosphatidyl ethanolamine in a ratio of 2:1. The purified glycosomal fraction had a very low DNA content of 0.18 microgram/mg protein. No DNA molecules were observed that could not have been derived from contaminating mitochondrial or nuclear debris.

Animals↗
PubMed1997

A cysteine endopeptidase isolated from castor bean endosperm microbodies processes the glyoxysomal malate dehydrogenase precursor protein.

A plant cysteine endopeptidase with a molecular mass of 35 kD was purified from microbodies of germinating castor bean (Ricinus communis) endosperm by virtue of its capacity to specifically process the glyoxysomal malate dehydrogenase precursor protein to the mature subunit in vitro. Processing of the glyoxysomal malate dehydrogenase precursor occurs sequentially in three steps, the first intermediate resulting from cleavage after arginine-13 within the presequence and the second from cleavage after arginine-33. The endopeptidase is unable to remove the presequences of prethiolases from rape (Brassica napus) glyoxysomes and rat peroxisomes at the expected cleavage site. Protein sequence analysis of N-terminal and internal peptides revealed high identity to the mature papain-type cysteine endopeptidases from cotyledons of germinating mung bean (Vigna mungo) and French bean (Phaseolus vulgaris) seeds. These endopeptidases are synthesized with an extended pre-/prosequence at the N terminus and have been considered to be processed in the endoplasmic reticulum and targeted to protein-storing vacuoles.

Amino Acid Sequence↗
PubMed1982

Three-dimensional structure of the crystalloid in the microbody of Kloeckera sp.: composite crystal model.

Electron microscopic investigations using the cryosectioning technique, together with electron diffraction, optical diffraction, and computer simulation, were carried out for the determination of the intrinsic structure of the crystalloid in the microbody of Kloeckera sp. The lattice images seen in the cryosections could be changed from one to another by tilting the specimen at an appropriate angle, the images obtained being well consistent with those obtained by computer simulation. The electron diffraction patterns also agreed with those obtained by optical diffraction. The results demonstrated that the crystalloid was composed of two different types of particles, large and small ones, arranged alternately and making up the composite crystal of rock salt structure. Large particles seemed to consist of alcohol oxidase molecules, while the small particles were presumably made up of catalase molecules.

Bacteria↗
PubMed1975

Matrical inclusions induced by clofibrate in hepatic microbodies of rats fed 2-acetylaminofluorene.

Abnormal inclusions in microbodies were induced by clofibrate in hepatocytes of hyperplastic liver nodules in rats fed 2-acetylaminofluorene. These were matrical tubules and plates, each with the same ultrastructural features as those reported previously by other investigators. A hyperplastic state of hepatocytes induced by hepatocarcinogens might be related to the formation of these inclusions in response to clofibrate.

Clofibrate↗
PubMed1991

The beta-oxidation system in catalase-free microbodies of the filamentous fungus Neurospora crassa. Purification of a multifunctional protein possessing 2-enoyl-CoA hydratase, L-3-hydroxyacyl-CoA dehydrogenase, and 3-hydroxyacyl-CoA epimerase activities.

A trifunctional beta-oxidation protein, designated TFP, was purified to apparent homogeneity from oleate-induced mycelia of Neurospora crassa. 2-Enoyl-CoA hydratase, L-3-hydroxyacyl-CoA dehydrogenase, and 3-hydroxyacyl-CoA epimerase activities copurified in constant ratios with this protein when crude extracts were subjected to cation-exchange, dye-ligand, and adsorption chromatography. Trifunctionality was substantiated by coinciding enzyme activity ratios during the last two purification steps and additional chromatographic steps. The enzyme was shown to be a 365-kDa tetramer of subunits with a molecular mass of 93 kDa. Several lines of evidence suggest that these subunits are identical. Monospecific antibodies raised against the homogenous protein specifically precipitated the three enzymatic activities of TFP. Immunoblotting of fractions obtained after sucrose density gradient centrifugation of a crude extract indicated that TFP was exclusively localized in glyoxysome-like microbodies. The beta-oxidation system of N. crassa is structurally related to those of peroxisomes despite the presence of an acyl-CoA dehydrogenase rather than an acyl-CoA oxidase. A mitochondrial 2-enoyl-CoA hydratase activity was separated from TFP and purified to apparent homogeneity. The absence of all other beta-oxidation activities from mitochondria suggests that this organelle and its 2-enoyl-CoA hydratase are not involved in fatty acid degradation in N. crassa.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1979

Subcellular localization of acyl coenzyme A: dihydroxyacetone phosphate acyltransferase in rat liver peroxisomes (microbodies).

Upon differential centrifugation of rat liver homogenate, the enzyme acyl-CoA:dihydroxyacetone-phosphate acyltransferase (EC 2.3.1.42) was found to be localized in the light mitochondrial (L) fraction which is enriched with lysosomes and peroxisomes. Peroxisomes were separated from lysosomes in a density gradient centrifugation using rats which were injected with Triton WR 1339. By comparing the enzyme distribution with the distribution of different marker enzymes, it was concluded that dihydroxyacetone phosphate acyltransferase is primarily localized in rat liver peroxisomes (microbodies). Similarly, the enzyme acyl dihydroxyacetone-phosphate:NADPH oxidoreductase (EC 1.1.1.101) was shown to be enriched in the peroxisomal fraction, although a portion of this reductase is also present in the microsomal fraction.

Acyltransferases↗
PubMed1997

[The coiled bodies and satellite microbodies of the oocyte nuclei in hibernating Rana temporaria frogs contain actin].

Immunocytochemical analysis of preparation of dispersed nuclei content in oocytes of III-IV stages of oogenesis, in terms of Dumont (1972), from hibernating grass frogs using monoclonal antibodies against actin, revealed two types of intranuclear structures containing this protein: coiled bodies (CB) and satellite microbodies (SM). Staining of these preparations with Rhodamin-phalloidin, known specifically to interact with fibrillar actin, did not reveal it in these structures. Results of our biochemical studies, using protease ESP32 specifically cutting only globular actin, are suggesting that both CB and SM contain globular actin. Gall et al. (1975) proposed that CB may be involved in assembling and sorting of small nuclear RNA for the three main RNA processing pathways: pre-mRNA splicing, pre-rRNA processing, and histone pre-mRNA 3'-end formation. Our finding of actin in CB allows a suggestion on actin involvement in the transport of RNA processing complexes from CB to some actual places where processing of RNA takes place. According to our previous data (Tsvetkov, Parfenov., 1994), SM participate in the karyosphere capsule formation. This process is preceded by SM fusion triggered presumably by actin.

Actins↗
PubMed1969

Distribution of peroxisomes (microbodies) in the nephron of the rat: a cytochemical study.

The distribution of peroxisomes (microbodies) in the rat nephron was studied cytochemically, using glutaraldehyde- or formaldehyde-fixed tissue, by means of alpha-hydroxy acid oxidase activity in light microscopy or oxidation of 3,3'-diaminobenzidine (DAB) at pH 9 in both light and electron microscopy.The two cytochemical methods show peroxisomes to be nearly sperical particles found only in cells of the proximal convoluted tubule. Lysosomes were identified in the same or parallel sections, with beta-glycerophosphate or 5'-cytidylic acid as substrate. They are found in all cells of the nephron. These cytochemical methods visualize the two organelles for light microscopy; they also permit unequivocal differentiation of all kidney peroxisomes from lysosomes in electron micrographs. Peroxisomes are larger and more reactive in the cells of the pars descendens (P(3) segment) of the proximal convolution, located in the outer medulla and medullary rays, than in the cells of the pars convoluta (P(1) and P(2) segments), situated in the cortex. In contrast, lysosomes are much smaller in the P(3) segment and larger and more reactive in the P(1) and P(2) segments. In all cells of the proximal convolution, peroxisomes tend to be concentrated nearer the base of the cells than do lysosomes. Mitochondria in P(3) cells also show low levels of DAB oxidation at pH 6, in contrast to those in P(1) and P(2) cells. The possibility is discussed that P(3) cells possess an extramitochondrial means of oxidation in which peroxisome oxidases play an important role.

Animals↗
PubMed1981

Nutritional Regulation of Organelle Biogenesis in Euglena: INDUCTION OF MICROBODIES.

Exposure of dark grown resting Euglena to ethanol produced a transient increase in the specific activity of the glyoxysomal enzyme malate synthase. Enzyme specific activity increased during the first 24 hours of ethanol treatment and then declined. Light exposure or malate addition failed to increase enzyme specific activity. The increase and decrease in enzyme specific activity represented changes in the amount of active enzyme. In both wild type cells and the plastidless mutant W(3)BUL, enzyme levels were always higher in the dark than in the light.The specific activity of the peroxisomal enzyme glycolate dehydrogenase began to increase 24 hours after dark grown resting Euglena were exposed to light. Ethanol, but not malate, prevented the increase and promoted a decrease in glycolate dehydrogenase levels. Cycloheximide produced a decline in enzyme levels similar to the decline produced by ethanol addition. Glycolate dehydrogenase was present in the plastidless mutant W(3)BUL indicating that it is coded in the nucleus and synthesized on cytoplasmic ribosomes. Streptomycin, a specific inhibitor of chloroplast protein synthesis and 3-(3,4-dichlorophenyl)-1,1-dimethylurea, an inhibitor of photosynthetic CO(2) fixation, inhibited the photoinduction of glycolate dehydrogenase while having no effect on the photoinduction of NADP dependent glyceraldehyde-3-phosphate dehydrogenase, another light induced, nuclear coded, cytoplasmically synthesized enzyme. Taken together, these results suggest that microbodies are continually synthesized in resting Euglena and their enzyme complement is determined through substrate induction of glyoxysomal and peroxisomal enzymes.

Journal Article↗
PubMed1984

Enzymes of beta-Oxidation in Different Types of Algal Microbodies.

The algae Mougeotia and Eremosphaera were used for isolation of microbodies with the characteristics of leaf peroxisomes and unspecialized peroxisomes, respectively. In both types of organelles, the following enzymes of the beta-oxidation pathway were determined: acyl-CoA oxido-reductase, enoyl-CoA hydratase, and 3-hydroxyacyl-CoA dehydrogenase. There are indications that the peroxisomal oxidoreductase of both algae is a H(2)O(2)-forming oxidase rather than a dehydrogenase.The enzymes enoyl-CoA hydratase and acyl-CoA oxidoreductase are located also in the mitochondria from Eremosphaera but not from Mougeotia. The mitochondrial acyl-CoA oxidizing enzyme was found to be a dehydrogenase. The specific activities of acyl-CoA oxidase and enoyl-CoA hydratase are lower than in spinach leaf peroxisomes. However, the activity of 3-hydroxyacyl-CoA dehydrogenase in the peroxisomes of both algae is almost 2-fold higher. The capability for degradation of fatty acids is a common feature of all different types of peroxisomes from algae.

Journal Article↗
PubMed1994

Ultrastructure of goat testes: crystalloid in the microbody of Sertoli cells.

During the morphological study of goat spermatogenesis, an electron dense core was noticed in the microbody of the Sertoli cell in adult animals. By means of a goniometer apparatus fitted to the electron microscope, tilting 30 degrees unidirection, the dense core frequently displayed a characteristic checker pattern as a crystalloid or crystal. The size of the lattices in the crystalloid was found to be 6.6 nm lattice rods with 16.7 nm intervals (n = 48). In this report, the structure and function of the crystalloid construction is discussed; and the results suggested, as did former reports, that it may be a kind of peroxisome.

Aging↗
PubMed1982

Fine structure and cytochemistry of peroxisomes (microbodies) Leptomonas samueli.

Leptomonas samueli possesses in its cytoplasm a membrane-bounded organelle which can reach a length of 2.8 microns and a diameter of 0.2 microns. Catalase activity, which is inhibited by 3-amino-1, 2, 4-triazole, was detected at the ultrastructural level in the matrix of the organelle by using an alkaline diaminobenzidine medium. Freeze-fracture studies showed the presence of a large number of intramembranous particles on both the P and the E faces of the membrane of the organelle. Based on these data as well as on previous observations, it is suggested that the trypanosomatids possess an organelle that can be considered to be a peroxisome.

Animals↗
PubMed1975

The isolation and characterization of peroxisomes (microbodies) from baker's yeast, Saccharomyces cerevisiae.

Peroxisomes were isolated form derepressed (lactose grown) Saccharomyces cerevisiae cells following homogenization with a "Merkenschlager" cell mill (at 0 degrees C using glass beads). Catalase and urate oxidase, along with low activities of D-amino acid oxidase and L-alpha-hydroxyacid oxidase (glycollate oxidase), were associated with the peroxisomes. No catalase activity was present in glucose repressed cells. When protoplasts prepared from derepressed cells were used for peroxisome isolation, catalase activity was not sedimentable through gradients. Apparently peroxisomes were destroyed as the cells became fermentative during protoplast preparation. The distribution of glyoxylate cycle enzymes was examined. Isocitrate lyase was not sedimentable, suggesting that, if the enzyme is peroxisome-associated, it is either readily released of present in a labile second class of peroxisomes. Low activities of malate dehydrogenase and citrate synthetase were found in peroxisome fractions from gradients, but may represent mitochondrial contamination. Citrate synthetase was not found associated with a low-density particle as had been previously reported.

Alcohol Oxidoreductases↗