EC Number   |
Reaction |
Reference |
|---|
    2.5.1.61 | 4 porphobilinogen + H2O = hydroxymethylbilane + 4 NH3 |
catalytic cycle, cofactor assembly and tetrapyrrole chain polymerization mechanism, C261 is involved, residues D99 and R167 are essential for activity, overview |
661042 |
| 2.5.1.61 | 4 porphobilinogen + H2O = hydroxymethylbilane + 4 NH3 |
four molecules of the pyrrole porphobilinogen are condensed to form the linear tetrapyrrole preuroporphyrinogen (hydroxymethylbilane). Hydrolysis of the linkage between the first substrate moiety and the cofactor releases the tetrapyrrole product preuroporphyrinogen |
737341 |
| 2.5.1.61 | 4 porphobilinogen + H2O = hydroxymethylbilane + 4 NH3 |
mechanism |
489928 |
| 2.5.1.61 | 4 porphobilinogen + H2O = hydroxymethylbilane + 4 NH3 |
reaction mechanism with active site residues R11, D84 and R176 that appear to be involved in controlling crucial steps during tetrapyrrole, detailed interaction analysis, overview. The compactness of the overall protein decreases progressively with addition of each pyrrole ring. domains move apart while the cofactor turn region moves towards the second domain, thus creating space for the pyrrole rings added at each stage. Residues of the flexible active site loop play a significant role in its modulation. During this movement, loop residue D50 interacts with R149 and K55 interacts with Q243, E305 and V306 with an occupancy of 41% along the trajectory. Upon removal of hydroxymethylbilane, the structure of the enzyme gradually relaxes to resemble its initial stage structure, indicating its readiness to resume a new catalytic cycle |
739392 |
| 2.5.1.61 | 4 porphobilinogen + H2O = hydroxymethylbilane + 4 NH3 |
The enzyme works by stepwise addition of pyrrolylmethyl groups until a hexapyrrole is present at the active centre. The terminal tetrapyrrole is then hydrolysed to yield the product, leaving a cysteine-bound dipyrrole on which assembly continues. In the presence of a second enzyme, EC 4.2.1.75 uroporphyrinogen-III synthase, which is often called cosynthase, the product is cyclized to form uroporphyrinogen-III. If EC 4.2.1.75 is absent, the hydroxymethylbilane cyclizes spontaneously to form uroporphyrinogen I |
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