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An intracellular organelle found in all eukaryotes except the archezoa (original lifeforms). In electron micrographs, peroxisomes appear round with a diameter of 0.1–1.0 micrometer, although there is evidence that in some mammalian tissues peroxisomes form an extensive reticulum (network). They contain more than 50 characterized enzymes and perform many biochemical functions, including detoxification. See Cell organization, Enzyme

Peroxisomes are important for lipid metabolism. In humans, the β-oxidation of fatty acids greater than 18 carbons in length occurs in peroxisomes. In yeast, all fatty acid β-oxidation occurs in peroxisomes. Peroxisomes contain the first two enzymes required for the synthesis of plasmalogens. Peroxisomes also play important roles in cholesterol and bile acid synthesis, purine and polyamine catabolism, and prostaglandin metabolism. In plants, peroxisomes are required for photorespiration. See Lipid metabolism, Photorespiration

A number of recessively inherited peroxisomal disorders have been described and grouped into three categories. Group I is the most severe and is characterized by a general loss of peroxisomal function. Many of the enzymes normally localized to the peroxisome are instead found in the cytosol. Among the diseases found in group I are Zellweger syndrome, neonatal adrenoleukodystrophy, and infantile Refsum disease. Patients with these disorders usually die within the first years after birth and exhibit neurological and hepatic (liver) dysfunction, along with craniofacial dysmorphism (malformation of the cranium and the face). Groups II and III peroxisomal disorders are characterized by a loss of peroxisomal function less severe than in group I.

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.


(cell and molecular biology)
Any of a subclass of microbodies that contain at least four enzymes involved in the metabolism of hydrogen peroxide.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Peroxisome Proliferator-activated receptor gamma (PPARI3), a nuclear receptor of the ligand-activated transcription factor family, can regulate gene transcription.
Review of the expression of peroxisome pro-liferator-activated receptors alpha (PPAR alpha), beta (PPAR beta), and gamma (PPAR gamma) in rodent and human development.
Molecular recognition of fatty acids by peroxisome proliferator activated receptors.
Peroxisome proliferator-activated receptors and their ligands: nutritional and clinical implications-a review.
The initial PPAR (PPAR[alpha]) was cloned as a nuclear receptor from a mouse-liver genetic (cDNA) library that was activated by several endogenous and xenobiotic compounds known as peroxisome proliferators.
Caption: Figure 2: SLC15A3 is located at lysosomes, late endosome, and peroxisome. Confocal microscopy observation of HeLa cells transfected with SLC15A3-GFP (green) and lysosome tracker (a), ER tracker (b), endogenous Rab5 (c), endogenous Rab7 (d), endogenous Rab11 (e), and RFP-PXMP2 (peroxisome tracker) (f).
Zellweger Syndrome (ZS) is a rare disease that takes a part in peroxisome biogenesis disorders.
The team found that medium-chain fatty alcohols could be produced in yeast by targeted expression of fatty acyl-CoA reductase, or TaFAR, in the peroxisome of Saccharomyces cerevisiae.
The protein Pex11b is associated with the membrane that surrounds the peroxisome, an organelle that helps to free energy from food.
Editor's Note: As possible protective mechanisms for DHEA, the authors note that the hormone is a peroxisome proliferator-activated receptor (PPAR) alpha agonist, as are fibrate drugs currently used to treat high triglyceride levels.
TZDs bind avidly to Peroxisome proliferator-activated receptor gamma (PPAR[gamma] agonists) and the activation of PPAR[gamma] by these drugs influences a number of genes expressed which are involved in lipid and glucose metabolism and preadipocyte differentiation.

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