Uroporphyrinogen III Synthetase

**Definition:** An enzyme that catalyzes the cyclization of hydroxymethylbilane to yield UROPORPHYRINOGEN III and water. It is the fourth enzyme in the 8-enzyme biosynthetic pathway of HEME, and is encoded by UROS gene. Mutations of UROS gene result in CONGENITAL ERYTHROPOIETIC PORPHYRIA.

**Tree numbers:** - D08.811.520.241.300.950

**Synonyms:** - Cosynthase - Uroporphyrinogen III Cosynthetase - Uroporphyrinogen Isomerase - Uroporphyrinogen-III Synthase