reaction 3 of heme synthesis
location: cytosolenzyme: porphobilinogen deaminaseit is a condensation reaction. Four molecules of porphobilinogen are linked to make a linear tetrapyrrole (pre-uroporphyingen). 4 NH4+ are released.
Reaction 3 of heme synthesis is the conversion of hydroxymethylbilane (HMB) to uroporphyrinogen III (URO III). This reaction is catalyzed by the enzyme uroporphyrinogen synthase (UROS) and it takes place in the cytoplasm of the cell.
UROS catalyzes the condensation of four molecules of HMB to form a linear tetrapyrrole called uroporphyrinogen-I (URO-I). This intermediate isomerizes spontaneously to form uroporphyrinogen III (URO III). In the process, hydroxyl groups on two of the pyrrole rings are moved to adjacent positions.
The reaction requires the presence of a divalent cation such as magnesium or manganese, which binds to the enzyme and helps to stabilize the reaction intermediate. The reaction also requires energy in the form of ATP, which is used to drive the condensation and is hydrolyzed in the process.
Uroporphyrinogen III is an important intermediate in the heme biosynthetic pathway since it serves as the precursor for the next reaction, which involves the insertion of a central iron atom to form protoporphyrin IX. Heme is then synthesized from protoporphyrin IX through a series of additional reactions.
More Answers:
Heme Synthesis: The Vital Role of Ferrochelatase in Inserting Iron for Essential Protein FunctionUnderstanding the Crucial Role of Reactions 5 and 6 in Heme Synthesis: From PBG to HMB
Understanding the Essential Role of Uroporphyrinogen Decarboxylase in Heme Synthesis and its Link to Porphyria