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Porphobilinogen (PBG) is an organic compound that occurs in living organisms as an intermediate in the biosynthesis of porphyrins, which include critical substances like hemoglobin and chlorophyll. [ 1 ]
Porphobilinogen deaminase (hydroxymethylbilane synthase, or uroporphyrinogen I synthase) is an enzyme (EC 2.5.1.61) that in humans is encoded by the HMBS gene. Porphobilinogen deaminase is involved in the third step of the heme biosynthetic pathway.
Aminolevulinic acid dehydratase (porphobilinogen synthase, or ALA dehydratase, or aminolevulinate dehydratase) is an enzyme (EC 4.2.1.24) that in humans is encoded by the ALAD gene. [ 5 ] [ 6 ] Porphobilinogen synthase (or ALA dehydratase , or aminolevulinate dehydratase ) synthesizes porphobilinogen through the asymmetric condensation of two ...
This deficiency prevents heme synthesis, which can not be completed and the metabolite porphobilinogen accumulates in the cytoplasm. [ 17 ] AIP is an autosomal dominant porphyria resulting in about 50% normal activity of the affected enzyme. [ 18 ]
Two molecules of dALA are then combined by porphobilinogen synthase to give porphobilinogen (PBG), which contains a pyrrole ring. Four PBGs are then combined through deamination into hydroxymethyl bilane (HMB), which is hydrolysed to form the circular tetrapyrrole uroporphyrinogen III. This molecule undergoes a number of further modifications.
HMB is generated from four molecules of porphobilinogen by the enzyme porphobilinogen deaminase: [2] The enzyme uroporphyrinogen III synthase closes the chain to form uroporphyrinogen III : [ 2 ] Uroporphyrinogen III is a porphyrinogen , which is a class of compounds with the hexahydroporphine macrocycle .
Porphobilinogen, a trisubstituted pyrrole, is the biosynthetic precursor to many natural products such as heme. [ 4 ] Pyrroles are components of more complex macrocycles, including the porphyrinogens and products derived therefrom, including porphyrins of heme , the chlorins , bacteriochlorins, and chlorophylls .
Aminolevulinic acid dehydratase deficiency porphyria (also known as Doss porphyria, [1] plumboporphyria, [1] or ADP [2]) is an extremely rare autosomal recessive metabolic disorder that results from inappropriately low levels of the enzyme delta-aminolevulinic acid dehydratase (), which is required for normal heme synthesis.