Author: Gianpiero Pescarmona
Date: 11/07/2011


Peroxisomes (also called microbodies) are organelles found in virtually all eukaryotic cells. They are particles of about 100-500 nm with a single membrane that surrounds an electron dense matrix

They are involved in different activities:

  • catabolism of very long chain fatty acids, branched chain fatty acids, D-amino acids, polyamines
  • biosynthesis of plasmalogens, etherphospholipids critical for the normal function of mammalian brains and lungs.
  • in liver cells, detoxify alcohol and other harmful compounds by transferring hydrogen directly to oxygen (oxidases that generate the harmful H2O2).
  • hydrogen peroxide (a common byproduct of cellular metabolism) degradation by Catalase.
  • synthesis of unsaturated fatty acid
  • production of bile acids
  • It is still debated if peroxisomes are involved in isoprenoid and cholesterol synthesis in animals

More details..


Peroxisomes at Molecular Expression

In order to carry out their activities, peroxisomes use significant amounts of oxygen and also contain approximately 10% of the total activity of two enzymes in the pentose phosphate pathway, which is important for NADPH synthesis.

This characteristic of the organelles would have been extremely important millions of years ago, before cells contained mitochondria.

Peroxisome content


The paracrystalline electron-dense inclusions are composed of the enzyme urate oxidase (not in man and prymates)

The peroxisomal enzyme Catalase degrades H2O2 by the reaction:
2 H2O2 � 2 H2O + O2

Import into Peroxisome

All peroxisomal proteins are synthesized at free ribosomes and are post-translationally transferred to the cytosol and imported into the peroxisomes. To this end, the newly synthesized proteins contain so-called peroxisomal targeting signals (PTSs) that are recognized by cytosolic receptor proteins for binding and guidance of the cargo to the peroxisomal membrane, a process that requires a number of additional proteins. Almost all matrix proteins have a type 1 PTS at their carboxyl terminus, specifically recognized by a receptor called Pex5p. Pex5p then binds to Pex13p, which is an integral membrane protein of the peroxisome.

from Dr. Ralf Erdmann site

Peroxisomes genesis

Peroxisomes are organelles that probably derive from the endoplasmic reticulum as donor organelle.

from The Peroxisome Biogenesis crew

Peroxisomes in Health and Disease

Peroxisome Biogenesis: Something Old, Something New, Something Borrowed 2010

Peroxisome Function

Fatty Acids > 20 catabolism

Peroxisomal oxidation stops at 8 carbon atoms, so the octanoyl-CoA and acetyl-CoA products of peroxisomal lipid breakdown are converted to the corresponding carnitine derivatives and shuttled across to the mitochondria to complete their conversion to carbon dioxide and water.

from Integration & Compartmentation of Metabolism, dr. J.A. Illingworth

FAD is electron acceptor for peroxisomal Acyl-CoA Oxidase, which catalyzes the first oxidative step of the pathway. The resulting FADH2 is reoxidized in the peroxisome producing hydrogen peroxide:

FADH2 + O2 � FAD + H2O2

Brain Peroxisomes

Axons need glial peroxisomes, 2007

Peroxisomes Number Regulation

from Michael J. Schell : We are investigating the molecules that regulate the transcription of genes that control peroxisome proliferation. We use a combination of cell biology, molecular biology, and microscopy to understand the pathways controlling peroxisome number and function. This research has medical relevance to metabolic disorders, neuronal migration, myelination, and Alzheimer's disease. We try to control peroxisome numbers in astrocytes via drugs that regulate cholesterol homeostasis in cells

2011-07-12T12:40:11 - Gianpiero Pescarmona

Exp Dermatol. 1996 Feb;5(1):49-56.
Lipoperoxidase activity of Pityrosporum: characterisation of by-products and possible rôle in pityriasis versicolor., 1996
De Luca C, Picardo M, Breathnach A, Passi S.
San Gallicano Dermatological Institute, Rome, Italy.
Modification of pigmentation and damage of melanocytes are characteristic features of skin colonisation of Pityrosporum orbiculare hyphae in pityriasis versicolor (PV). The yeast is lipophylic and lipid-dependent, capable of oxidising unsaturated lipid components of skin surface, i.e., unsaturated fatty acids, cholesterol and squalene (SQ). The oxidation of unsaturated fatty acids gives rise to dicarboxylic acids (DA) which behave, in vitro, as competitive inhibitors of tyrosinase. In this work, we further investigate the oxidase activity of Pityrosporum in vitro, by evaluating (a) the generation of lipoperoxides in cultures supplemented with fatty acids at various degrees of unsaturation; (b) the mechanism of SQ oxidation; © the chemical characteristics of some by-products of lipoperoxidation; (d) the formation of peroxisomes in fungal cells. In cultures supplemented with the saturated palmitic acid (C16:0) and monounsaturated oleic acid (C18:1 n-9), low amounts of lipoperoxides were detected by a spectrophotometric test, whereas in cultures supplemented with di-unsaturated linoleic acid (C18:2 n-6), significant concentrations were found. Gas chromatography-mass spectrometry analyses showed the generation of linoleic acid hydroperoxides both in Pityrosporum cultures and following incubation of acetone powder of the fungus with the unsaturated fatty acid, indicating the presence of a lipoxygenase activity in the fungus. In cultures supplemented with linoleic acid plus SQ, and increase of lipoperoxide generation was observed and trans-trans farnesal and squalene epoxides have been identified. Electron microscopic examinations have evidenced peroxisomes in cells grown in the presence of linoleic acid, whereas they were not detected in cultures supplemented with oleic acid and palmitic acid. The metabolic activities of peroxisomes, through the formation of hydrogen peroxide and the subsequent generation of hydroxyl radicals, may account for the peroxidation of SQ, which is not a substrate of lipoxygenase. Following these results, we propose a mechanism for DA generation by Pityrosporum metabolism and hypothesize that the lipoperoxidation process induced by lipoxygenase activity of the fungus may be the key to understanding the clinical appearance of skin manifestation of PV.

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