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)

The immunogold labeling technique has been extremely useful in investigation of the structure and function of peroxisomes. In this report a few examples of the application of this technique with significant implications in the field are briefly reviewed. The problem of extra-peroxisomal catalase, the subject of long controversy between the biochemists and cytochemists, was settled with the immunogold technique, which unequivocally revealed the presence of that enzyme not only in the cytoplasm, but also in the euchromatin region of nucleus, in addition to peroxisomes. On the other hand, lactate dehydrogenase, a typical cytoplasmic protein, has also been shown recently to be present in peroxisomes and to be involved in the reoxidation of NADH produced by the peroxisomal beta-oxidation system. The immunogold technique has revealed several distinct compartments in the matrix of mammalian peroxisomes: urate oxidase in the crystalline cores, alpha-hydroxy acid oxidase B in the marginal plates and D-amino acid oxidase in a non-crystalline condensed region of matrix. The specific alterations of peroxisomal proteins are reflected in their immunolabeling density with gold particles. Quantitation of gold-label by automatic image analysis has revealed that the induction of lipid beta-oxidation enzyme proteins by diverse hypolipidemic drugs is initiated and more pronounced in the pericentral regions of the liver lobule. Finally, immunogold labeling with an antibody to 70 kDa peroxisomal membrane protein has identified a novel class of small peroxisomes that initially incorporate radioactive amino acids more efficiently than regular peroxisomes and thus may represent early stages in the biogenesis of peroxisomes.
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PMID:Contributions of the immunogold technique to investigation of the biology of peroxisomes. 885 70

We showed recently the plasticity of the peroxisomal compartment in the human hepatoblastoma cell line HepG2 as evidenced by the presence of elongated tubular peroxisomes measuring up to 5 microm next to much smaller spherical or rod-shaped ones (0.1-0.3 microm). Since the occurrence of tubular peroxisomes in a given cell in culture is synchronized, with neighboring cells containing either small spherical or elongated tubular peroxisomes, cell counting of immunofluorescence preparations stained for catalase was used for the quantitative assessment of the dynamics of the peroxisomal compartment and the factors regulating this process. Initial studies revealed that the formation of tubular peroxisomes is primarily influenced by the cell density as well as by lipid- and protein-factors in fetal calf serum, being independent of an intact microtubular network. Biochemical studies showed that the occurrence of tubular peroxisomes correlated with the expression of the mRNA for 70 kDa peroxisomal membrane protein (PMP70), but not with that of matrix proteins. By cultivation of cells in serum- and protein-free media specific factors were identified which influenced the formation of tubular peroxisomes. Among several growth factors tested, nerve growth factor (NGF) was the most potent one inducing tubular peroxisomes and its effect was blocked by K252b, a specific inhibitor of neurotrophin receptor pathway, suggesting the involvement of signal transduction in this process. Furthermore, from several polyunsaturated fatty acids (PUFA) which all induced tubular peroxisomes, the arachidonic acid (AA) was the most potent one. Our observations suggest that tubular peroxisomes are transient structures in the process of rapid expansion of the peroxisomal compartment which are induced either by specific growth factors or by polyunsaturated fatty acids both of which are involved in intracellular signaling.
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PMID:Tubular peroxisomes in HepG2 cells: selective induction by growth factors and arachidonic acid. 954 66

Immuno-isolation is a powerful technique for the isolation of cells as well as subcellular organelle populations based on their antigenic properties. We have established a method for immuno-isolation of peroxisomes (PO) from both rat liver and the human hepatoblastoma cell line HepG2 using magnetic beads as solid support. A polyclonal antibody raised against the cytoplasmic C-terminal 10 amino acids of the rat 70 kDa peroxisomal membrane protein was covalently bound to magnetic beads (Dynabeads M-450). The coated beads were incubated with a light mitochondrial fraction and the organelle-bead complexes formed were separated by magnetic sorting in a free-flow system without pelleting the complexes during the isolation procedure. Scanning electron microscopy revealed decoration of beads with particles measuring 150-400 nm in diameter. The particles were identified as PO by catalase cytochemistry and biochemically by marker enzyme analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) as well as immunoblotting for specific detection of peroxisomal matrix, core and membrane proteins. The functional significance of PO in man is emphasized by the existence of inherited diseases such as the Zellweger syndrome in which intact PO are lacking, but peroxisomal remnants called "ghosts" are observed instead. Peroxisomal disorders are usually studied using skin fibroblast cell lines derived from afflicted patients and immuno-magnetic separation may prove particularly useful for the investigation of such cultured cells and for further elucidation of the pathogenesis of fatal peroxisomal disorders.
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PMID:Immuno-isolation of highly purified peroxisomes using magnetic beads and continuous immunomagnetic sorting. 966 84

The mutant Chinese hamster ovary (CHO) cell line Z78/C has defective peroxisome assembly due to a missense mutation in PEX2, the gene which encodes the 35 kDa peroxisomal integral membrane protein. In humans, PEX2 mutations are responsible for complementation group 10 of the human peroxisome biogenesis disorders (PBD), a genetically heterogeneous group of lethal, autosomal recessive diseases including the Zellweger syndrome and related phenotypes. To develop additional cellular models for Zellweger syndrome, we produced a series of new mutant CHO cell clones in the same complementation group as Z78/C (Z2, Z7, Z22, and Z105). As expected, expression of human PEX2 restores peroxisomal biogenesis in all of these clones. Surprisingly, expression of the human 70 kDa peroxisomal membrane protein (PMP70) also restores peroxisome biogenesis in these same CHO cell clones. We confirmed this effect of PMP70 expression on peroxisome biogenesis by determining the subcellular latency of catalase, the immunohistochemical localization of catalase and the beta-oxidation of very long chain fatty acids (VLCFA). By contrast, expression of a mutant allele of PMP70 identified in a patient with Zellweger syndrome did not restore peroxisome biogenesis in the PEX2-deficient CHO cell clones. Our results indicate that overexpression of PMP70 suppresses the phenotype of PEX2 gene mutations. These observations suggest a functional interaction between PEX2 and PMP70 in the peroxisome membrane.
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PMID:Restoration of PEX2 peroxisome assembly defects by overexpression of PMP70. 976 53

In rat liver, peroxisome proliferators induce profound changes in the number and protein composition of peroxisomes, which upon subcellular fractionation is reflected in heterogeneity in sedimentation properties of peroxisome populations. In this study we have investigated the time course of induction of the peroxisomal proteins catalase, acyl-CoA oxidase (ACO) and the 70 kDa peroxisomal membrane protein (PMP70) in different subcellular fractions. Rats were fed a di(2-ethylhexyl)phthalate (DEHP) containing diet for 8 days and livers were removed at different time-points, fractionated by differential centrifugation into nuclear, heavy and light mitochondrial, microsomal and soluble fractions, and organelle marker enzymes were measured. Catalase was enriched mainly in the light mitochondrial and soluble fractions, while ACO was enriched in the nuclear fraction (about 30%) and in the soluble fraction. PMP70 was found in all fractions except the soluble fraction. DEHP treatment induced ACO, catalase and PMP70 activity and immunoreactive protein, but the time course and extent of induction was markedly different in the various subcellular fractions. All three proteins were induced more rapidly in the nuclear fraction than in the light mitochondrial or microsomal fractions, with catalase and PMP70 being maximally induced in the nuclear fraction already at 2 days of treatment. Refeeding a normal diet quickly normalized most parameters. These results suggest that induction of a heavy peroxisomal compartment is an early event and that induction of 'small peroxisomes', containing PMP70 and ACO, is a late event. These data are compatible with a model where peroxisomes initially proliferate by growth of a heavy, possibly reticular-like, structure rather than formation of peroxisomes by division of pre-existing organelles into small peroxisomes that subsequently grow. The various peroxisome populations that can be separated by subcellular fractionation may represent peroxisomes at different stages of biogenesis.
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PMID:Differential induction of peroxisomal populations in subcellular fractions of rat liver. 1134 45

Peroxisomes are ubiquitous organelles required for several metabolic functions. Their dysfunction is responsible for a group of human inherited disorders. In the search for endogenous factors regulating the peroxisomal compartment in normal liver, we treated female rats with dehydroepiandrosterone (DHEA) and 25-hydroxycholecalciferol for 1 and 6 days. Relative transcription levels of 39 selected genes were evaluated by real-time quantitative RT-PCR analysis. Catalase (peroxisomal marker)-specific activity was assayed in total liver homogenate and peroxisomes were visualized by catalase localization. DHEA induced peroxisome proliferation and raised catalase specific activity. Expression levels of 16 (of which 11 were peroxisomal) genes were altered. Pex 11, acyl-CoA oxidase,l - andd -multifunctional enzyme, thiolase 1, phytanoyl-CoA hydroxylase, 70 kDa peroxisomal membrane protein and very long chain acyl-CoA synthetase were upregulated, three others were downregulated. Vitamin D caused downregulation of six genes. Administration of vitamin D to peroxisomal disorder patients may be contraindicated. The adrenocortical hormone DHEA is a potential natural regulator of the peroxisomal compartment. Its therapeutic use in X-linked adrenoleukodystrophy, some other beta-oxidation defects and classical Refsum should be considered.
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PMID:Modulation of the peroxisomal gene expression pattern by dehydroepiandrosterone and vitamin D: therapeutic implications. 1247 88