Uroporphyrinogen III

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Uroporphyrinogen III
Identifiers
MeSH Uroporphyrinogen+III
Properties
C40H44N4O16
Molar mass 836.795 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Uroporphyrinogen III is a tetrapyrrole, the first macrocyclic intermediate in the biosynthesis of heme, chlorophyll, vitamin B12, and siroheme. It is a colorless compound, like other porphyrinogens.[1]

Structure

The

molecular structure of uroporphyrinogen III can be described as a hexahydroporphine core, where each pyrrole ring has the hydrogen atoms on its two outermost carbons replaced by an acetic acid group (−CH2−COOH, "A") and a propionic acid
group (−CH2−CH2−COOH, "P"). The groups are attached in an asymmetric way: going around the macrocycle, the order is AP-AP-AP-PA.

Biosynthesis and metabolism

In the general

uroporphyrinogen-III cosynthase.[2][3]


Biosynthesis of Uroporphyrinogen-III from pre-uroporphyrinogen

The conversion entails a reversal of the last

hydroxyl
−OH with a hydrogen atom of the first ring.

In the biosynthesis of hemes and chlorophylls, uroporphyrinogen III is converted into coproporphyrinogen III by the enzyme uroporphyrinogen III decarboxylase. In the biosynthesis of sirohemes, uroporphyrinogen III is converted by two methyl transferases to dihydrosirohydrochlorin, which is subsequently oxidized sirohydrochlorin, a precursor to the siroheme prosthetic group.

Medical significance

If uroporphyrinogen-III synthase is not present or inactive, the hydroxymethylbilane will spontaneously cyclise into the

congenital erythropoietic porphyria[3]

See also

References

  1. S2CID 4177167
    .
  2. ISBN 978-0-470-04867-2
    .
  3. ^
    doi:10.1046/j.1365-2796.2000.00618.x
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