Uroporphyrinogens are cyclic

tetrapyrroles Tetrapyrroles are a class of chemical compounds that contain four pyrrole or pyrrole-like rings. The pyrrole/pyrrole derivatives are linked by ( =- or -- units), in either a linear or a cyclic fashion. Pyrroles are a five-atom ring with four car ...

with four propionic acid groups ("P" groups) and four acetic acid groups ("A" groups). There are four forms, which vary based upon the arrangements of the "P" and "A" groups (in clockwise order): * In the "I" variety (i.e.

uroporphyrinogen I Uroporphyrinogen I is an isomer of uroporphyrinogen III, a metabolic intermediate in the biosynthesis of heme. A type of porphyria is caused by production of uroporphyrinogen I instead of III. Biosynthesis and metabolism In living organisms, ur ...

), the order repeats four times: AP-AP-AP-AP. * In the "III" variety (i.e.

uroporphyrinogen III 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. Structure The molecular structure of uroporphy ...

), the fourth is reversed: AP-AP-AP-PA. *:This is the most common form. In the synthesis of

porphyrin Porphyrins ( ) are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH−). The parent of porphyrin is porphine, a rare chemical com ...

, it is created from the linear tetrapyrrole

hydroxymethylbilane Hydroxymethylbilane, also known as preuroporphyrinogen, is an organic compound that occurs in living organisms during the synthesis of porphyrins, a group of critical substances that include haemoglobin, myoglobin, and chlorophyll. The name is of ...

by the enzyme

uroporphyrinogen III synthase Uroporphyrinogen III synthase () is an enzyme involved in the metabolism of the cyclic tetrapyrrole compound porphyrin. It is involved in the conversion of hydroxymethyl bilane into uroporphyrinogen III Uroporphyrinogen III is a tetrapyrrole, ...

, and is further converted into

coproporphyrinogen III Coproporphyrinogen III is a metabolic intermediate in the biosynthesis of many compounds that are critical for living organisms, such as hemoglobin and chlorophyll. It is a colorless solid. The compound is a porphyrinogen, a class of compounds ...

by the enzyme uroporphyrinogen III decarboxylase. * The "II" and "IV" varieties can be created synthetically, but do not appear in nature.

External links

* Biomolecules {{biochem-stub