Uroporphyrinogen III is the first cyclic metabolic intermediate in the biosynthesis of heme. The linear precursor, hydroxymethylbilane is generated from four porphobilinogen (PBG) molecules by the third enzyme in the synthesis, hydroxymethylbilane synthase (or porphobilinogen deaminase). When the linear chain of four PBGs (hydroxymethylbilane) is released from hydroxymethylbilane synthase, the next enzyme in the haem biosynthesis, uroporphyrinogen-III synthase, converts hydroxymethylbilane into the cyclic uroporphyrinogen III. This product is subsequently converted into coproporphyrinogen III by the enzyme uroporphyrinogen III decarboxylase. However, if there is no uroporphyrinogen-III synthase present, the linear tetrapyrrole will be spontaneous cyclised into Uroporphyrinogen I, which is then converted into coproporphyrinogen I, also by uroporphyrinogen III decarboxylase; The difference between the two forms, is the arrangements of the four propionic acid (\"P\" groups) and the four acetic acid groups (\"A\" groups), where non-enzyamtically conversion into uroporphyrinogen I results in an AP-AP-AP-AP symmetry, whereas the enzymatically conversion into uroporphyrinogen III lead to a reversed AP-group and hence an AP-AP-AP-PA arrangement.

CAS：1976-85-8
中文别名：
英文别名：3-[7,12,18-tris(2-carboxyethyl)-3,8,13,17-tetrakis(carboxymethyl)-5,10,15,20,21,22,23,24-octahydroporphyrin-2-yl]propanoic acid;uro\'gen III;uroporphyrinogen iv;uroporphyrinogen-III;uroprophyrinogen III;uroporphyrin III;
分子式：C40H44N4O16
分子量：836.795
精确质量：836.275
Psa：361.56
Logp：2.2528

密度：1.575g/cm3
沸点：1163.6ºC at 760mmHg
闪点：657.5ºC
折射率：1.685
蒸汽压：0mmHg at 25°C