Presence of heterogeneous peroxisomal populations in the rat nervous tissue

Peroxisomes were purified from the nervous tissue of 14-day-old rats by means of a Nycodenz gradient. Peroxisomal enzymes exhibited different sedimentation patterns: dihydroxyacetone phosphate acyl-transferase equilibrates at 1.142 g/ml together with the first peak of catalase; palmitoyl-CoA oxidase and d-amino acid oxidase activities are mainly recovered at 1.154 g/ml; the second peak of catalase is found at 1.175 g/ml. Morphological and semi-quantitative analyses of immunogold-labelled peroxisomes reveal profound heterogeneity of the particles. Very small (=0.2 μm diameter), electron dense vesicles containing catalase or thiolase, but devoid of other tested enzymes, are preferentially found in the light region, together with larger (>0.2 <0.3 μm) and less electron dense palmitoyl-CoA oxidase-positive peroxisomes. At intermediate density (1.154 g/ml) peroxisomes of more uniform size (0.25–0.27 μm), containing palmitoyl-CoA oxidase or thiolase with or without catalase are preferentially found. This population extends toward the densest region of the gradient, where very large d-amino acid oxidase-containing peroxisomes are also found. In this region, smaller peroxisomes, often polymorphic, which are catalase- and thiolase-positive and d-amino acid oxidase/palmitoyl-CoA oxidase-negative, are also observed. The possibility that the heterogeneity of neural peroxisomes may reflect both cellular heterogeneity and ongoing peroxisomal biogenesis is discussed.     

Peroxisomes in digestive gland cells of the mussel Mytilus galloprovincialis Lmk. Biochemical, ultrastructural and immunocytochemical characterization.

The present study was undertaken because of the paucity of information on peroxisomes in molluscs and the increasing importance of these organisms as sensitive indicators of environmental pollution. Peroxisomes were identified by electron microscopy in all three main cell types of the digestive gland of the bivalve mollusc Mytilus galloprovincialis Lmk. They stained weakly with the alkaline diaminobenzidine reaction but showed distinct immunolabeling with an antibody against mammalian catalase by the postembedding protein A-gold procedure. In addition, mussel digestive gland peroxisomes were isolated by differential and metrizamide-density gradient centrifugation, and a 30-fold enrichment of catalase and a 20-fold enrichment of palmitoyl-CoA oxidase was obtained over the initial homogenate. By Western blotting, isolated peroxisomes crossreacted with antibodies to catalase and, furthermore, specific and prominent labeling of isolated peroxisomes was also demonstrated in thin sections incubated with anti-catalase antibodies. These observations establish that peroxisomes in molluscan digestive gland contain the peroxisomal marker enzymes catalase and acyl-CoA oxidase and that they can be labeled by cytochemical and immunocytochemical techniques. Further studies of alterations of molluscan peroxisomes by environmentally relevant xenobiotics are warranted.     

Immunocytochemical localization of urate oxidase, fatty acyl-CoA oxidase, and catalase in bovine kidney peroxisomes

We investigated the localization of urate oxidase, peroxisomal fatty acyl-CoA oxidase, and catalase in bovine kidney by immunoblot analysis and protein A-gold immunocytochemistry, using the respective polyclonal monospecific antibodies raised against the enzymes purified from rat liver. By immunoblot analysis, these three proteins were detected in bovine kidney and bovine liver homogenates. Subcellular localization of these three enzymes in kidney was ascertained by protein A-gold immunocytochemical staining of Lowicryl K4M-embedded tissue. Peroxisomes in bovine kidney cortical epithelium possessed crystalloid cores or nucleoids, which were found to be the exclusive sites of urate oxidase localization. The limiting membrane, the marginal plate, and the matrix of renal peroxisomes were negative for urate oxidase staining. In contrast, catalase and fatty acyl-CoA oxidase were found in the peroxisome matrix. These results demonstrate that, unlike rat kidney peroxisomes which lack urate oxidase, peroxisomes of bovine kidney contain this enzyme as well as peroxisomal fatty acyl-CoA oxidase.     

Acyl-CoA synthetase and the peroxisomal enzymes of beta-oxidation in human liver. Quantitative analysis of their subcellular localization.

The presence of acyl-CoA synthetase (EC 6.2.1.3) in peroxisomes and the subcellular distribution of beta-oxidation enzymes in human liver were investigated by using a single-step fractionation method of whole liver homogenates in metrizamide continuous density gradients and a novel procedure of computer analysis of results. Peroxisomes were found to contain 16% of the liver palmitoyl-CoA synthetase activity, and 21% and 60% of the enzyme activity was localized in mitochondria and microsomal fractions respectively. Fatty acyl-CoA oxidase was localized exclusively in peroxisomes, confirming previous results. Human liver peroxisomes were found to contribute 13%, 17% and 11% of the liver activities of crotonase, beta-hydroxyacyl-CoA dehydrogenase and thiolase respectively. The absolute activities found in peroxisomes for the enzymes investigated suggest that in human liver fatty acyl-CoA oxidase is the rate-limiting enzyme of the peroxisomal beta-oxidation pathway, when palmitic acid is the substrate.     

Peroxisomes in molluscs, characterization by subcellular fractionation combined with western blotting, immunohistochemistry, and immunocytochemistry

Peroxisomes of the digestive glands of mussels, Mytilus galloprovincialis Lmk, were investigated by immunoblotting and immunohistochemistry using rabbit antibodies against several mammalian hepatic peroxisomal proteins. Western blot analysis of main subcellular fractions revealed immunoreactive polypeptides with molecular weights comparable to those of the corresponding mammalian hepatic proteins. They could be localized to the peroxisomal matrix in the case of catalase, multifunctional enzyme (PH), and palmitoyl-CoA oxidase (AOX), and to the peroxisomal membrane in respect to PMP 70. The purification of peroxisomes by metrizamide density gradient centrifugation revealed the existence of two subpopulations with densities of 1.16 and 1.20 g cm^–3 exhibiting different protein compositions. In paraffin sections, positive immunolabeling for catalase was distributed along the apical cytoplasm of the epithelia of digestive ducts and stomach and throughout the cytoplasm of digestive tubule cells. The peroxisomal β-oxidation enzymes, AOX and PH, also appeared predominantly in the ducts and the stomach epithelia with a weaker immunolabeling in the tubules. At the electron microscopic level a clear labeling with gold particles was observed in the peroxisomal matrix with the anti-guinea pig catalase antibody. In addition to peroxisomes, the anti-PH antibody also labeled the mitochondria. The similarity in the protein composition of molluscan and mammalian peroxisomes as revealed by the present study indicates that those proteins have been well conserved in evolution suggesting that functionally peroxisomes in molluscs could also be involved in the metabolism of lipids and in detoxification of xenobiotics. Thus, the antibodies tested could provide useful tools for detection of peroxisomal induction in molluscan biomonitoring programs for the assessment of aquatic environmental pollution. Accepted: 19 October 1999     

Immunolocalization of four antioxidant enzymes in digestive glands of mollusks and crustaceans and fish liver

The aim of this work was to determine the immunolocalization of the antioxidant enzymes catalase, Cu,Zn-superoxide dismutase (SOD), Mn-SOD, and glutathione peroxidase (GPX) in the bivalve mollusks Mytilus galloprovincialis and Crassostrea sp., the crab Carcinus maenas, and the teleostean fish Mugil cephalus. By immunoblotting, crossreactivity between antibodies and the corresponding proteins in the digestive gland/hepatopancreas of invertebrates and the fish liver was demonstrated. Immunohistochemical studies showed that the stomach epithelium was strongly immunostained for catalase in mollusks. In crabs, ducts showed stronger immunostaining than tubules and in mullet hepatocytes the reaction appeared in discrete granules corresponding to peroxisomes. With regard to Cu,Zn-SOD, the apex of the tubule cells in mussels and crabs was distinctly immunostained, whereas in oysters the reaction was more marked in ducts and in mullet liver a uniform diffuse cytoplasmic staining was found. Mn-SOD was strongly positive in mollusk and crab ducts and in mullet periportal hepatocytes. Finally, GPX was not detected in mussels while in oysters a slight reaction was noted in all cell types. In crabs, connective tissue cells and the apex of duct cells were immunostained, but in mullet liver only erythrocytes appeared reactive. Immunoelectron microscopy revealed that catalase was localized in peroxisomes with a dense labeling in fish and less intense labeling in invertebrates. Cu,Zn-SOD was mainly a cytosolic protein although additional positive subcellular sites (peroxisomes, nuclei) were also observed, while Mn-SOD was restricted to mitochondria. GPX was localized in the cytosol, nucleus, and lysosomes, occurring also in peroxisomes of the fish liver. The results presented here provide a basis for future application of the immunodetection techniques to study the possible differential induction of antioxidant enzymes in aquatic organisms subjected to oxidative stress as a result of exposure to environmental pollutants.     

Cytochemical and immunocytochemical study on the peroxisomes of rat liver after administration of a hypolipidemic drug, MLM-160

After administration of a hypolipidemic drug, MLM-160, to male rats, liver peroxisomes were studied by biochemical, cytochemical, and immunocytochemical methods. The activities of D-amino acid oxidase, glycolate oxidase, and urate oxidase increased 2 to 3-fold by the treatment. The increase of the oxidases was confirmed by immunoblotting analysis. By light microscopy, immunoreaction for catalase was present in the cytoplasmic granules of hepatocytes. The stained granules formed some clusters and overlapped each other after MLM-160 treatment. However, immunostaining for D-amino acid oxidase and urate oxidase was present in discrete fine granules which did not overlap each other. By electron microscopy, many peroxisomes showed ring-like extensions and cavitation of the matrix, often giving the appearance of a peroxisome-within-a-peroxisome. In many cases, these unusual peroxisomes seemed to be interconnected with each other. Within the peroxisomes, the catalase was localized in the matrix. Urate oxidase was associated with the crystalloid cores. D-amino acid oxidase was localized focally in a small part of the matrix where the catalase was mostly negative. In conclusion, the administration of MLM-160 to male rats induces some peroxisomal oxidases, accompanying the appearance of unusual peroxisomes. The precise localization of peroxisomal enzymes suggested that there are subcompartments within the liver peroxisomes as shown in rat kidney peroxisomes.     

Investigation of peroxisomal lipid beta-oxidation enzymes in guinea pig liver peroxisomes by immunoblotting and immunocytochemistry.

We investigated the immunoreactivity of the peroxisomal lipid beta-oxidation enzymes acyl-CoA oxidase, trifunctional protein, and thiolase in guinea pig liver and compared it with that of homologous proteins in rat, using immunoblotting of highly purified peroxisomal fractions and monospecific antibodies to rat proteins. In addition, the immunocytochemical localization of beta-oxidation enzymes in guinea pig liver was compared with that of catalase. All antibodies showed crossreactivity between the two species, indicating that these peroxisomal proteins have been well conserved, although all exhibited some differences with respect to molecular size and, in the case of acyl-CoA oxidase, in frequency of the immunoreactive bands. In the latter case, a distinct second band in the 70 KD range was observed in guinea pig, in addition to the regular band due to subunit A present in rat liver. This novel band could be due either to trihydroxycoprostanoyl-CoA oxidase or to the non-inducible branched chain fatty acid oxidase described recently. All three beta-oxidation enzymes were immunolocalized by light and electron microscopy to the matrix of peroxisomes, in contrast to catalase, which is also found in the cytoplasm and the nucleus of hepatocytes in guinea pig liver.     

Catalase in guinea pig hepatocytes is localized in cytoplasm, nuclear matrix and peroxisomes

We have compared the intracellular localization of catalase and another peroxisomal marker enzyme, alpha-hydroxy acid oxidase (HAOX), in the livers of guinea pig and rat using immunoelectron microscopy and subcellular fractionation combined with immunoblotting and enzyme activity determination. Antibodies against both enzymes were raised in rabbits and their specificities established by immunoblotting. By immunoelectron microscopy, gold particles representing antigenic sites for catalase were found in guinea pig hepatocytes not only in peroxisomes but also in the cytoplasm and the nuclear matrix. In rat liver, however, catalase was localized exclusively in peroxisomes with no cytoplasmic labeling. Moreover, in both species HAOX was found only in peroxisomes. Subcellular fractionation revealed that purified peroxisomes from both species contained comparable levels of each, catalase and HAOX activities. The total catalase activity, however, was substantially higher in guinea pig and most of this excess catalase was in the cytosolic fraction with some activity also in nuclei. In rat liver, 30 to 40% of both enzymes and in guinea pig liver 30% of HAOX were recovered in the supernatant fraction implying that the fragility of peroxisomes in both species is quite comparable. These observations establish the occurrence of extraperoxisomal catalase in guinea pig liver. The catalase in the cytoplasm and nucleus of liver parenchymal cells is most probably involved in scavenging of H2O2, protecting the cell against toxic and mutagenic effects of this noxious agent.     

Hepatic enzymes, CoASH and long-chain acyl-CoA in subcellular fractions as affected by drugs inducing peroxisomes and smooth endoplasmic reticulum

1. The activities of acyl-CoA hydrolase, catalase, urate oxidase and peroxisomal palmitoyl-CoA oxidation as well as the protein content and the level of CoASH and long-chain acyl-CoA were measured in subcellular fractions of liver from rats fed diets containing phenobarbital (0.1% w/w) or clofibrate (0.3% w/w). 2. Whereas phenobarbital administration resulted in increased microsomal protein, the clofibrate-induced increase was almost entirely attributed to the mitochondrial fraction with minor contribution from the light mitochondrial fraction. 3. The specific activity of palmitoyl-CoA hydrolase in the microsomal fraction was only slightly affected while the mitochondrial enzyme was increased to a marked extent (3-4-fold) by clofibrate. 4. Phenobarbital administration mainly enhanced the microsomal palmitoyl-CoA hydrolase. 5. The increased long-chain acyl-CoA and CoASH level observed after clofibrate treatment was mainly associated with the mitochondrial, light mitochondrial and cytosolic fractions, while the slight increase in the levels of these compounds found after phenobarbital feeding was largely of microsomal origin. 6. The findings suggest that there is an intraperoxisomal CoASH and long-chain acyl-CoA pool. 7. The specific activity of palmitoyl-CoA hydrolase, catalase and peroxisomal palmitoyl-CoA oxidation was increased in the lipid-rich floating layer of the cytosol-fraction. 8. The changes distribution of the peroxisomal marker enzymes and microsomal palmitoyl-CoA hydrolase after treatment with hypolipidemic drugs may be related to the origin of peroxisomes.     

Cytochemical localization of catalase and several hydrogen peroxide-producing oxidases in the nucleoids and matrix of rat liver peroxisomes

Synopsis The distribution of catalase, amino acid oxidase, -hydroxy acid oxidase, urate oxidase and alcohol oxidase was studied cytochemically in rat hepatocytes. The presence of catalase was demonstrated with the conventional diaminobenzidine technique. Oxidase activities were visualized with methods based on the enzymatic or chemical trapping of the hydrogen peroxide produced by these enzymes during aerobic incubations.All enzymes investigated were found to be present in peroxisomes. Catalase activity was found in the peroxisomal matrix, but also associated with the nucleoid. After staining for oxidase activities the stain deposits occurred invariably in the peroxisomal matrix as well as in the nucleoids. In all experiments the activity of both catalase and the oxidases was confined to the peroxisomes. The presence of a hydrogen peroxide-producing alcohol oxidase was demonstrated for the first time in peroxisomes in liver cells.The results imply that the enzyme activity of the nucleoids of rat liver peroxisomes is not exclusively due to urate oxidase. The nucleoids obviously contain a variety of other enzymes that may be more or less loosely associated with the insoluble components of these structures.     

Peroxisomes and peroxisomal functions in muscle. Studies with muscle cells from controls and a patient with the cerebro-hepato-renal (Zellweger) syndrome

In the present study we investigated peroxisomal functions in cultured human muscle cells from control subjects and from a patient with the Zellweger syndrome, a genetic disease characterized by the absence of morphologically distinguishable peroxisomes in liver and kidney. In homogenates of cultured muscle cells from control subjects, catalase is contained within subcellular particles, acyl-CoA:dihydroxyacetonephosphate acyltransferase activity is present and palmitoyl-CoA can be oxidized by a peroxisomal beta-oxidative pathway; these findings are indicative of the presence of peroxisomes in the cells. In homogenates of cultured muscle cells from the patient with the Zellweger syndrome, acyl-CoA:dihydroxyacetonephosphate acyltransferase activity was deficient, peroxisomal beta-oxidation of palmitoyl-CoA was impaired and catalase was not particle-bound. These findings indicate that functional peroxisomes are absent in muscle from patients with the Zellweger syndrome. We conclude that cultured human muscle cells can be used as a model system to study peroxisomal functions in muscle and the consequences for this tissue of a generalized dysfunction of peroxisomes.     

The effect of clofibrate on amphibian hepatic peroxisomes.

Liver peroxisomes of two anuran amphibian species, Rana esculenta and Xenopus laevis, were studied in untreated and in clofibrate-treated adults by means of complementary technical approaches, ie, ultrastructural cytochemistry, cell fractionation and marker enzyme activity assays. In untreated adults, hepatic peroxisomes were found to be very scarce in Xenopus when compared to Rana. Activities of catalase, D-amino acid oxidase and of the three first enzymes of the peroxisomal beta-oxidation system were detected in the light mitochondrial fractions enriched in peroxisomes and prepared from livers of both species. Administration of clofibrate at a daily dose level of 60 mg (Rana) and 90 mg (Xenopus) during ten days induced a drastic peroxisome proliferation in Rana hepatocytes but had no visible effect on the hepatic peroxisomal population of Xenopus. The catalase activity and the peroxisomal beta-oxidation system of liver cells were enhanced in Rana as well as in Xenopus. The hepatic D-amino acid oxidase specific activity was increased in Rana whereas it remained rather constant in Xenopus. Taking advantage of the behaviors of Rana and Xenopus hepatic peroxisomes, the molecular mechanisms of clofibrate induction are now investigated in the target liver cells of the two amphibian species.     

Immunocytochemical localization of delta 3, delta 2-enoyl-CoA isomerase in rat liver. The effects of di-(2-ethylhexyl)phthalate, a peroxisome proliferator

Immunocytochemical localization of delta 3, delta 2-enoyl-CoA isomerase (isomerase) was investigated in rat liver. Livers of di-(2-ethylhexyl)phthalate (DEHP)-treated or untreated rats were perfusion-fixed and embedded in Epon or Lowicryl K4M. By light microscopy, reaction deposits for the enzyme were present in the cytoplasmic granules of hepatocytes and interlobular bile duct epithelium. Weak staining was noted in sinus-lining cells. After administration of DEHP, the granular staining of the hepatocytes was markedly enhanced, whereas the staining reaction of the sinus-lining cells decreased. The isomerase staining pattern was quite similar to that of long-chain acyl-CoA dehydrogenase (a mitochondrial marker), but different from that of catalase (a peroxisomal marker). Under electron microscopy, gold particles for isomerase were seen to be confined mainly to mitochondria of the hepatocytes, the bile duct epithelial cells and sinus-lining cells. Peroxisomes were weakly labeled. After DEHP administration, the peroxisomes were markedly induced, but the mitochondria were not. Quantitative analysis showed that the induction of the peroxisomal isomerase was only 2-fold whereas the mitochondrial isomerase was enhanced about 5-fold, 40 times as high as the peroxisomal enzyme. The results show that the mitochondria are the main intracellular site for isomerase and the peroxisomes a minor site. The mitochondrial isomerase of the rat liver is markedly induced by peroxisome proliferators, DEHP and clofibrate.     

Immunocytochemical demonstration of peroxisomal enzymes in human kidney biopsies

Peroxisomes are particularly abundant in the proximal tubules of the mammalian kidney. We describe the immunocytochemical localization of catalase and three peroxisomal lipid beta-oxidation enzymes: acyl-CoA oxidase, bifunctional protein (enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase) and 3-ketoacyl-CoA thiolase, in human renal biopsies fixed with glutaraldehyde and embedded in Epon. For light microscopy of semithin sections, satisfactory immunostaining required removal of the resin and controlled proteolytic digestion followed by the indirect immunoperoxidase technique. Brief etching of ultrathin sections with alkoxide followed by the protein A-gold method were used for electron microscopic localization of the enzymes. The immunoreactive peroxisomes were distinctly visualized in proximal tubular epithelial cells with no staining of any other cell organelles. The results establish the presence of catalase and of peroxisomal lipid beta-oxidation system proteins in human kidney. The immunocytochemical procedure described herein provides a simple approach for the investigation of peroxisomal structure and function in human renal biopsies processed for ultrastructural studies.     

Enzyme activities of isolated hepatic peroxisomes from genetically lean and obese male mice.

Hepatic peroxisomes have been isolated on isopycnic sucrose gradients from white mice [HA(ICR)] and lean and obese (C57BL/6J) mice. Nearly all of the catalase activity was in the peroxisomal fraction. The activity for β-oxidation of palmitoyl-CoA was about threefold higher per milligram of protein in the isolated peroxisomal fraction or per gram of liver from the obese mouse compared to its lean littermates. Glycerol-3-phosphate dehydrogenase activity also was higher in the peroxisomes and cytoplasm of the obese mouse. The matrix enzymes of the organelles, catalase and urate oxidase of the peroxisome and glutamate dehydrogenase of the mitochondria, had similar activities per gram of liver from either lean or obese mice. Membrane components, NADPH: cytochrome c reductase of the microsomes and β-hydroxybutyrate dehydrogenase of the mitochondria, had lower activities in the obese mouse in inverse proportion to the larger size of the liver.     

Evidence that peroxisomal acyl-CoA synthetase is located at the cytoplasmic side of the peroxisomal membrane.

1. Subfractionation by isopycnic density-gradient centrifugation in self-generating Percoll gradients of peroxisome-rich fractions prepared by differential centrifugation confirmed the presence of acyl-CoA synthetase in peroxisomes. Peroxisomes did not contain nicotinamide or adenine nucleotides other than CoA. 2. The gradient fractions most enriched in peroxisomes were pooled and the peroxisomes sedimented by centrifugation, resulting in a 50-fold-purified peroxisomal preparation as revealed by marker enzyme analysis. 3. Palmitate oxidation by intact purified peroxisomes was CoA-dependent, whereas palmitoyl-CoA oxidation was not, demonstrating that the peroxisomal CoA was available for the thiolase reaction, located in the peroxisomal matrix, but not for acyl-CoA synthetase. This suggests that the latter enzyme is located at the cytoplasmic side of the peroxisomal membrane. 4. Additional evidence for this location of peroxisomal acyl-CoA synthetase was as follows. Mechanical disruption of purified peroxisomes resulted in the release of catalase from the broken organelles, but not of acyl-CoA synthetase, indicating that the enzyme was membrane-bound. Acyl-CoA synthetase was not latent, despite the fact that at least one of its substrates appears to have a limited membrane permeability, as evidenced by the presence of CoA in purified peroxisomes. Finally, Pronase, a proteinase that does not penetrate the peroxisomal membrane, almost completely inactivated the acyl-CoA synthetase of intact peroxisomes.     

Structure, composition, physical properties, and turnover of proliferated peroxisomes. A study of the trophic effects of Su-13437 on rat liver

Peroxisome proliferation has been induced with 2-methyl-2-(p-[1,2,3,4-tetrahydro-1-naphthyl]-phenoxy)-propionic acid (Su-13437). DNA, protein, cytochrome oxidase, glucose-6-phosphatase, and acid phosphatase concentrations remain almost constant. Peroxisomal enzyme activities change to approximately 165%, 50%, 30%, and 0% of the controls for catalase, urate oxidase, L-alpha-hydroxy acid oxidase, and D-amino acid oxidase, respectively. For catalase the change results from a decrease in particle-bound activity and a fivefold increase in soluble activity. The average diameter of peroxisome sections is 0.58 +/- 0.15 mum in controls and 0.73 +/- 0.25 mum after treatment. Therefore, the measured peroxisomal enzymes are highly diluted in proliferated particles. After tissue fractionation, approximately one-half of the normal peroxisomes and all proliferated peroxisomes show matric extraction with ghost formation, but no change in size. In homogenates submitted to mechanical stress, proliferated peroxisomes do not reveal increased fragility; unexpectedly, Su-13437 stabilizes lysosomes. Our results suggest that matrix extraction and increased soluble enzyme activities result from transmembrane passage of peroxisomal proteins. The changes in concentration of peroxisomal oxidases and soluble catalase after Su-13437 allow the calculation of their half-lives. These are the same as those found for total catalase, in normal and treated rats, after allyl isopropyl acetamide: about 1.3 days, a result compatible with peroxisome degradation by autophagy. A sequential increase in liver RNA concentration, [14C]leucine incorporation into DOC-soluble proteins and into immunoprecipitable catalase, and an increase in liver size and peroxisomal volume per gram liver, characterize the trophic effect of the drug used. In males, Su-13437 is more active than CPIB, another peroxisome proliferation-inducing drug; in females, only Su-13437 is active.     

Induction, identification, and cell-free translation of mRNAs coding for peroxisomal proteins in Candida tropicalis

Peroxisomes have been purified from Candida tropicalis grown on oleic acid and shown to be nearly pure by marker enzyme analysis, electron microscopy, and comparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. They contain approximately 20 polypeptides, among which acyl-CoA oxidase, trifunctional hydratase-dehydrogenase-epimerase, and catalase have been identified. Rabbit antisera have been elicited that react with these three proteins. When C. tropicalis is grown on alkanes, a dozen mRNAs are strikingly induced. Nine of the 12 induced mRNAs code for polypeptides that comigrate in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with peroxisomal proteins, among which three have been identified immunochemically as the acyl-CoA oxidase, the trifunctional protein, and catalase. These results indicate that some genes coding for peroxisomal proteins are strongly expressed during growth of C. tropicalis on alkanes. The data are consistent with evidence in other species that peroxisomes form by the post-translational incorporation of newly made proteins into pre-existing peroxisomes, generally without proteolytic processing, followed by peroxisome division.     

Biogenesis and cytochemistry of unspecialized peroxisomes in root cortical cells of Yucca torreyi L

Microbodies containing bipyramidal crystalline nucleoid inclusions occur within every cortical cell in roots of Yucca torreyi. Reaction product deposition attributable to catalase, glycolate oxidase, and urate oxidase activities are cytochemically localized to Yucca root microbodies and classifies them as unspecialized peroxisomes on the basis of their enzyme complement and tissue origin. Crystalline nucleoids do not stain for glycolate or urate oxidase activities, appearing as negatively-stained inclusions, but are apparently reactive for catalase activity. Development of unspecialized peroxisomes in Yucca roots is consistent with all evidence for glyoxysome and leaf-type peroxisome biogenesis from ER. Dilated ends of ER cisternae accumulate cytochemically detectable glycolate oxidase activity. After considerable dilation, paracrystalline precursors to nucleoids form within the bulge, and the inclusion enlarges to comprise the majority of peroxisomal volume. Peroxisomes that are not attached to ER are observed with high voltage electron microscopy and in serial thin sections, implying that eventually the budding peroxisomes are vesiculated. The functions of these unspecialized peroxisomes are suggested based upon cytochemical detection of their partial enzyme complement and their spatial and developmental timing relationships within developing Yucca root cortical parenchyma cells.