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The following scheme summarizes the biosynthesis of porphyrins, with references by EC number and the OMIM database. The porphyria associated with the deficiency of each enzyme is also shown: Heme B biosynthesis pathway and its modulators. Major enzyme deficiences are also shown.
In the typical porphyrin biosynthesis pathway, four molecules of porphobilinogen are concatenated by carbons 2 and 5 of the pyrrole ring (adjacent to the nitrogen atom) into hydroxymethyl bilane by the enzyme porphobilinogen deaminase, also known as hydroxymethylbilane synthase.
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.
Other organisms produce ALA through a three enzyme pathway known as the C5 pathway. ALA is synthesized through the condensation of glycine and succinyl-CoA. In humans, transcription of ALA synthase is tightly controlled by the presence of Fe 2+-binding elements, to prevent accumulation of porphyrin intermediates in the absence of iron. There ...
The last step is mediated by the enzyme protoporphyrinogen oxidase. Protoporphyrin IX is an important precursor to biologically essential prosthetic groups such as heme, cytochrome c, and chlorophylls. As a result, a number of organisms are able to synthesize this tetrapyrrole from basic precursors such as glycine and succinyl-CoA, or glutamic ...
Acute intermittent porphyria (AIP) is a rare metabolic disorder affecting the production of heme resulting from a deficiency of the enzyme porphobilinogen deaminase. It is the most common of the acute porphyrias. [1] [2] [3]
Porphyrins interact with iron, absorbing photons to create reactive oxygen species is the mechanism of action causing the itchy, painful blisters of PCT. [7] The reactive oxygen species consume the skin antioxidants beta-carotene, vitamin E, and vitamin C. Supplementation of these three vitamins reduces the oxidation and potentially diminishes ...
CPOX is an enzyme involved in the sixth step of porphyrin metabolism it catalyses the oxidative decarboxylation of coproporphyrinogen III to proto-porphyrinogen IX in the haem and chlorophyll biosynthetic pathways. [5] [11] The protein is a homodimer containing two internally bound iron atoms per molecule of native protein. [12]