Hydroxymethylbilane
Template:Short description Template:Chembox 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 often abbreviated as HMB.
Structure
The compound is a substituted bilane, a chain of four pyrrole rings interconnected by methylene bridges Template:Chem2. The chain starts with a hydroxymethyl group Template:Chem2 and ends with a hydrogen, in place of the respective methylene bridges. The other two carbon atoms of each pyrrole cycle are connected to an acetic acid group Template:Chem2 and a propionic acid group Template:Chem2, in that order.[1]
Metabolism
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. In the absence of the enzyme, the compound undergoes spontaneous cyclization and becomes uroporphyrinogen I.[3][4]