Peroxisomes (also called microbodies) are organelles found in virtually all eukaryotic cells. They are involved in the catabolism of very long chain fatty acids, branched chain fatty acids, D-amino acids, polyamines, and biosynthesis of plasmalogens, i.e. ether phospholipids critical for the normal function of mammalian brains and lungs.
It is well known that diets rich in n-3 play a favorable role in preventing and ameliorating cardiovascular diseases. The effects of dietary fish oil on myocardial peroxisomes have not been described before. In heart homogenates of rats fed diets supplemented with partially hydrogenated marine oil and rapeseed oil, an induction of the peroxisomal beta-oxidation was observed. Catalase activity was also increased in these animals. Starvation, experimentally induced diabetes, and treatment with clofibrate or inhibitors of mitochondrial beta-oxidation all provoked an increase in peroxisomal beta-oxidation, catalase activity, and peroxisomal number in myocardium of rodents.
Peroxisomes had long been considered as relatively unimportant organelles until it was reported that peroxisomes were absent in the livers of patients with the cerebro-hepato-renal syndrome of Zellweger. Today it is known that at least 13 metabolic diseases are related to a deficiency in one or more peroxisomal enzymes. Besides severe clinical symptoms, an accumulation of the very long chain fatty acids is always observed in patients with an inborn error of peroxisomal &oxidation.
Peroxisomes house several powerful oxidative enzymes and contain most of the cell's catalase. Oxidative enzymes, as the name implies, use oxygen (O2), in this case to strip hydrogen from certain organic molecules. This reaction helps detoxify various wastes produced within the cell or foreign toxic compounds that have entered the cell, such as alcohol.
The major product generated in the peroxisome, hydrogen peroxide (H2O2), is formed by molecular oxygen and the hydrogen atoms stripped from [a] toxic molecule. Hydrogen peroxide is potentially destructive if allowed to accumulate or escape from the confines of the peroxisome.
Peroxisomes are specialized for carrying out oxidative reactions using molecular oxygen. They generate hydrogen peroxide, which they use for oxidative purposes—destroying the excess by means of the catalase they contain. Peroxisomes also have an important role in the synthesis of specialized phospholipids required for nerve cell myelination.
Peroxisomes differ from mitochondria and chloroplasts in many ways. Most notably, they are surrounded by only a single membrane, and they do not contain DNA or ribosomes. Like mitochondria and chloroplasts, however, peroxisomes are thought to acquire their proteins by selective import from the cytosol. But because they have no genome, all of their proteins must be imported. Peroxisomes thus resemble the [endoplasmic reticulum] in being a self-replicating, membrane-enclosed organelle that exists without a genome of its own.
Peroxisomes are similar in appearance to lysosomes, another type of microbody, but the two have very different origins. Lysosomes are generally formed in the Golgi complex, whereas peroxisomes self-replicate. Unlike self-replicating mitochondria, however, peroxisomes do not have their own internal DNA molecules. Consequently, the organelles must import the proteins they need to make copies of themselves from the surrounding cytosol. The importation process of peroxisomes is not yet well understood, but it appears to be heavily dependent upon peroxisomal targeting signals composed of specific amino acid sequences.
Microbodies are a diverse group of organelles that are found in the cytoplasm of almost all cells, roughly spherical, and bound by a single membrane. There are several types of microbodies, including lysosomes, but peroxisomes are the most common. All eukaryotes are comprised of one or more cells that contain peroxisomes. The organelles were first discovered by the Belgian scientist Christian de Duve, who also discovered lysosomes.
[Christian de Duve] won the Nobel Prize for Physiology or Medicine in 1974 for the discovery of lysosomes and peroxisomes, organelles within the cell. He is perhaps best known for his ideas about the origin of life on Earth, about which he has published widely and for the lay reader.
Among the other genes [Hill, leader of the Equine Exercise Genomics Group at University College Dublin] says play a role in thoroughbred performance are peroxisome proliferator-activated receptor-γ coactivator-1 alpha (PGC-1α), which is involved in skeletal muscle adaptation to exercise; pyruvate dehydrogenase kinase, isozyme 4 (PDK4), involved in glucose regulation, expression of which increased almost fourfold after sprints; and cytochrome c oxidase subunit 4 isoform 2 (COX 4I2), involved in respiration. Hill showed a single-nucleotide polymorphism—placed in the genome where a single nucleotide is altered—in this gene is "strongly associated" with elite sprint racing performance.