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A peroxisome (IPA: [pɛɜˈɹɒksɪˌsoʊm]) is a membrane-bound organelle (formerly known as a microbody), found in the cytoplasm of virtually all eukaryotic cells. Peroxisomes are oxidative organelles. Frequently, molecular oxygen serves as a co-substrate, from which hydrogen peroxide (H2O2) is then formed. Peroxisomes owe their name to hydrogen peroxide generating and scavenging activities. They perform key roles in lipid metabolism and the conversion of reactive oxygen species. Peroxisomes are involved in the catabolism of very long chain fatty acids, branched chain fatty acids, bile acid intermediates (in the liver), D-amino acids, and polyamines, the reduction of reactive oxygen species – specifically hydrogen peroxide – and the biosynthesis of plasmalogens, i.e., ether phospholipids critical for the normal function of mammalian brains and lungs. They also contain approximately 10% of the total activity of two enzymes (Glucose-6-phosphate dehydrogenase and 6-Phosphogluconate dehydrogenase) in the pentose phosphate pathway, which is important for energy metabolism. It is vigorously debated whether peroxisomes are involved in isoprenoid and cholesterol synthesis in animals. Other known peroxisomal functions include the glyoxylate cycle in germinating seeds ("glyoxysomes"), photorespiration in leaves, glycolysis in trypanosomes ("glycosomes"), and methanol and/or amine oxidation and assimilation in some yeasts.
Adrenoleukodystrophy (ALD) is a disease linked to the X chromosome. It is a result of fatty acid buildup caused by a defect in the very long chain of fatty acids transporter in peroxisomes, which then causes damage to the myelin sheath of the nerves, resulting in seizures and hyperactivity. Other symptoms include problems with speaking, listening, and understanding verbal instructions.
Zellweger syndrome is a rare congenital disorder characterized by the reduction or absence of functional peroxisomes in the cells of an individual. It is one of a family of disorders called Zellweger spectrum disorders which are leukodystrophies. Zellweger syndrome is named after Hans Zellweger (1909–1990), a Swiss-American pediatrician, a professor of pediatrics and genetics at the University of Iowa who researched this disorder.
Leukodystrophies are a group of usually inherited disorders characterized by degeneration of the white matter in the brain. The word leukodystrophy comes from the Greek roots leuko, "white", dys, "abnormal" and troph, "growth". The leukodystrophies are caused by imperfect growth or development of the myelin sheath, the fatty insulating covering around nerve fibers. Leukodystrophies may be classified as hypomyelinating or demyelinating diseases, depending on whether the damage is present before birth or occurs after. Other demyelinating diseases are usually not congenital and have a toxic or autoimmune cause.
Peroxisomal disorders represent a class of medical conditions caused by defects in peroxisome functions. This may be due to defects in single enzymes important for peroxisome function or in peroxins, proteins encoded by PEX genes that are critical for normal peroxisome assembly and biogenesis.
Rhizomelic chondrodysplasia punctata is a rare developmental brain disorder characterized by systemic shortening of the proximal bones, seizures, recurrent respiratory tract infections and congenital cataracts. The affected individuals have low levels of plasmalogens.
ABCD1 is a protein that transfers fatty acids into peroxisomes.
Infantile Refsum disease (IRD), is a rare autosomal recessive congenital peroxisomal biogenesis disorder within the Zellweger spectrum. These are disorders of the peroxisomes that are clinically similar to Zellweger syndrome and associated with mutations in the PEX family of genes. IRD is associated with deficient phytanic acid catabolism, as is Adult Refsum disease, but they are different disorders that should not be confused.
Peroxisomal targeting signal 1 receptor (PTS1R) is a protein that in humans is encoded by the PEX5 gene.
Peroxisome biogenesis factor 1, also known as PEX1, is a protein which in humans is encoded by the PEX1 gene.
Peroxisomal biogenesis factor 19 is a protein that in humans is encoded by the PEX19 gene.
ATP-binding cassette sub-family D member 3 is a protein that in humans is encoded by the ABCD3 gene.
Peroxisome assembly protein 12 is a protein that in humans is encoded by the PEX12 gene.
Peroxisome assembly factor 2 is a protein that in humans is encoded by the PEX6 gene. PEX6 is an AAA ATPase that localizes to the peroxisome. PEX6 forms a hexamer with PEX1 and is recruited to the membrane by PEX26.
Peroxisome biogenesis factor 10 is a protein that in humans is encoded by the PEX10 gene. Alternative splicing results in two transcript variants encoding different isoforms.
ATP-binding cassette sub-family D member 2 is a membrane pump/transporter protein that in humans is encoded by the ABCD2 gene.
Peroxisomal membrane protein PEX16 is a protein that in humans is encoded by the PEX16 gene.
Zellweger spectrum disorders are a group of rare disorders that create the same disease process. The subdivisions of this spectrum are hyperpipecolic acidemia, Infantile Refsum disease, neonatal adrenoleukodystrophy (NALD), and Zellweger syndrome. It can also be referred to as Peroxisomal Biogenesis Disorders, Zellweger Syndrome Spectrum, NALD, Cerebrohepatorenal Syndrome, and ZSS. It can affect many body organs, including the kidneys, eyes, and hearing. It is named after Hans Zellweger.
Heimler syndrome is a rare autosomal recessive condition characterized by sensorineural hearing loss, amelogenesis imperfecta, nail abnormalities and occasional or late-onset retinal pigmentation
NALD may refer to:
References
- ↑ RESERVED, INSERM US14-- ALL RIGHTS. "Orphanet: Neonatal adrenoleukodystrophy". www.orpha.net. Retrieved 17 March 2019.
- ↑ "#202370 Adrenoleukodystrophy, Autosomal Neonatal Form". Johns Hopkins University. Retrieved 2012-06-24.