Hydroxymethylbilane Synthase
An enzyme that catalyzes the tetrapolymerization of the monopyrrole PORPHOBILINOGEN into the hydroxymethylbilane preuroporphyrinogen (UROPORPHYRINOGENS) in several discrete steps. It is the third enzyme in the 8-enzyme biosynthetic pathway of HEME. In humans, deficiency in this enzyme encoded by HMBS (or PBGD) gene results in a form of neurological porphyria (PORPHYRIA, ACUTE INTERMITTENT). This enzyme was formerly listed as EC 4.3.1.8
Ammonia-Lyases
Uroporphyrinogen III Synthetase
Porphyria, Acute Intermittent
An autosomal dominant porphyria that is due to a deficiency of HYDROXYMETHYLBILANE SYNTHASE in the LIVER, the third enzyme in the 8-enzyme biosynthetic pathway of HEME. Clinical features are recurrent and life-threatening neurologic disturbances, ABDOMINAL PAIN, and elevated level of AMINOLEVULINIC ACID and PORPHOBILINOGEN in the urine.
Porphobilinogen
Uroporphyrinogens
Porphyrinogens which are intermediates in heme biosynthesis. They have four acetic acid and four propionic acid side chains attached to the pyrrole rings. Uroporphyrinogen I and III are formed from polypyrryl methane in the presence of uroporphyrinogen III cosynthetase and uroporphyrin I synthetase, respectively. They can yield uroporphyrins by autooxidation or coproporphyrinogens by decarboxylation.