uroporphyrinogen

See porphyrinogens.

- u. decarboxylase an enzyme that participates in heme biosynthesis; it catalyzes the decarboxylation of uroporphyrin III to produce coproporphyrinogen III; it also acts on uroporphyrin I; a deficiency of this enzyme will result in either porphyria cutanea tarda or hepatoerythropoietic porphyria.

- u. III cosynthase an enzyme in heme biosynthesis that participates in the formation of u. III; a deficiency of this protein results in congenital erythropoietic porphyria.

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uro·por·phy·rin·ogen .yu̇r-ō-.pȯr-fə-'rin-ə-jən n any of several porphyrins that can be converted to uroporphyrins or to a precursor of coproporphyrins

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uro·por·phy·rin·o·gen (u″ro-por″fə-rinґə-jən) a porphyrinogen (q.v.) in which each pyrrole ring has one acetate side chain and one propionate side chain; it is formed by condensation of four molecules of porphobilinogen. Four isomers are possible but only two exist naturally, types I and III; the latter is a functional intermediate in heme biosynthesis while the former is produced in an abortive side reaction.