Peroxisomes. En1954, Rodhin found in the proximal tubule of mouse kidney of small organelles which he called "Microbodies" 1962, Novikoff microperoxisomas discovered. Organelles are self-replicating and limited x 1 membrane, q is present in all eukaryotic cells containing the enzyme are pre q mitochondria are involved in: Control of lipid homeostasis by beta-oxidation. Conversion of cholesterol into bile salts (only in the liver). Plasmalogen biosynthesis (or esters, phospholipids). Cellular respiration. In plants, peroxisomes of seeds are responsible for the conversion of ac. acids into carbohydrates through the ac. glyoxylic. MORPHOLOGY AND COMPOSITION peroxisome No varies with cell type, are most abundant in liver and kidney. In the liver involved in the metabolism of colesterol or gluconeogénesis.Son ovoid organelles whose diameter ranges between 0.15 and 1.7 ?. They are limited by the peroxisomal membrane and contain a homogeneous matrix, a nucleoid and a marginal plate. The peroxisomal membrane has a tripartite structure. The matrix is moderately dense to electrons. The marginal plate is flat, linear, with a thickness of 8,5 nm and is characterized by its homogeneity and density. It is separated from the peroxisome membrane. Peroxisomes are arranged in a network. There are some very fine tubules that associate with each other. The canaliculi and peroxisomes have the same functions. In humans, peroxisomes are rarely homogeneous matrix and marginal plaques. The membrane of peroxisomes consists of a 30% lipid and 70% protein. Contains electron carriers, cytochrome P-450, cytochrome b, enzymes involved in lipid metabolism, oxidoreductases and Peroxin.
BIOGENESIS Peroxisomes are formed from preexisting peroxisomes. PEX genes are responsible for the assembly and maintenance of peroxisomes. Encode all matrix proteins and their membrane. PEX genes are controlled by peroxisomal proliferators. The Peroxin act as a shuttle between the cytosol and the peroxisomal membrane, in the cytosol, complexed with proteins carrying PTS1 or PTS2 signals. Peroxisomal biogenesis is associated with cell proliferation.
ROLE Catabolism: Degradation of purines. Participation in the beta-oxidation ac. acids. Degradation of alcohol. Degradation of cholesterol derivatives. Anabolism: Biosynthesis of lipid esters. (Plasmanogenos). Neoglucogénesis.Minicadena breathing.
Pathobiology In humans 17 have been described peroxisomal genetic diseases,15 of which are characterized by affecting the nervous system. These genetic diseases are recessive lethal diseases, and are due to mutation of one or more genes that encode enzymes peroxisómicas.son childhood diseases, generally are lethal during the first ten years of life. Affect less than one per 50,000 newborns. DISEASES OF GROUP A: They result from the absence of many peroxisomal enzymes. Zelwerger Disease: This syndrome is dominated by the following manifestations: craniofacial dysmorphism, bilateral cataracts, retinopathy, liver disease small renal cysts and dysplasia cerebral hypomyelination says. Adrenoleukodystrophy neonata: Disease X-linked genetic cause is a deficit The acyl-CoA axidasa. In its most severe form produces a condition of the CNS. Adrenal insufficiency may be the only clinical manifestation. This disease is also characterized by an accumulation of ac. very long chain fatty acids, caused by the absence of ß-oxidation in peroxisomes.Refsum disease. Hiperpipecólica acidemia. DISEASES OF GROUP B: Solo is represented by Rhizomelic chondrodysplasia punctate. This disease is characterized by a problem in the rhizomelic type growth (stunting of the proximal extremity), cataracts, calcification, ichthyosis (flaking skin). DISEASES OF GROUP C: Includes adrenoleukodystrophy and diseases caused by deficiency of a single peroxisomal enzyme. Adrenoleukodystrophy: Disease X-linked gene that is characterized biochemically by an accumulation of ac. very long chain fatty acids in the white matter of the nervous system, adrenal glands, cough fibroblasts and blood plasma. This condition is linked to the absence of VLCFA-CoA. It is the most common peroxisomal disease, affecting 1 in 15,000 males. Neurological symptoms from a cerebral demyelination of neurons and impairment of peripheral nerves and spinal cord.Refsum Disease: Is caused by a deficiency of dihydroxyacetone phosphate acyltransferase, and is characterized by problems at CNS and peripheral. Hyperoxaluria: It is due to mutation of a gene for peroxisomal AGT (alanita glyoxylate aminotransferase). This gap allows the glyoxylate is oxidized to oxalate. Calcium oxalate, very insoluble, secreted by the kidneys and cause kidney stones or nephrocalcin.