Uroporphyrin I (BioDeep_00000005941)

描述信息

Uroporphyrin is the porphyrin produced by oxidation of the methylene bridges in uroporphyrinogen. Uroporphyrins have four acetic acid and four propionic acid side chains attached to their pyrrole rings. The enzyme uroporphyrinogen I synthase catalyzes the formation of hydroxymethylbilane from four molecules of porphobilinogen. Uroporphyrinogen III cosynthase then catalyzes the conversion of hydroxymethylbilane into uroporphyrinogen III. Otherwise, hydroxymethylbilane cyclizes nonenzymatically to form uroporphyrinogen I. Uroporphyrinogen I and III yield their respective uroporphyrins via autooxidation or their respective coproporphyrinogens via decarboxylation. Excessive amounts of uroporphyrin I are excreted in congenital erythropoietic porphyria, and both uroporphyrin I and uroporphyrin III are excreted in porphyria cutanea tarda. Uroporphyrin I and III are the most common isomers. Under certain conditions, uroporphyrin I can act as a phototoxin, a neurotoxin, and a metabotoxin. A phototoxin leads to cell damage upon exposure to light. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of porphyrins are associated with porphyrias such as porphyria variegate, acute intermittent porphyria, porphyria cutanea tarda, and hereditary coproporphyria (HCP). There are several types of porphyrias (most are inherited). Hepatic porphyrias are characterized by acute neurological attacks (seizures, psychosis, extreme back and abdominal pain, and an acute polyneuropathy), while the erythropoietic forms present with skin problems (usually a light-sensitive blistering rash and increased hair growth). The neurotoxicity of porphyrins may be due to their selective interactions with tubulin, which disrupt microtubule formation and cause neural malformations (PMID: 3441503).
Uroporphyrin is the porphyrin produced by oxidation of the methylene bridges in uroporphyrinogen. They have four acetic acid and four propionic acid side chains attached to the pyrrole rings. Uroporphyrinogen I and III are formed from polypyrryl methane in the presence of uroporphyrinogen III cosynthetase and uroporphyrin I synthetase, respectively. They can yield uroporphyrins by autooxidation or coproporphyrinogens by decarboxylation.Excessive amounts of uroporphyrin I are excreted in congenital erythropoietic porphyria, and both types I and III are excreted in porphyria cutanea tarda.Uroporphyrin I and III are the most common isomers. [HMDB]

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