title: Purification and properties of the uroporphyrinogen decarboxylase from Rhodobacter sphaeroides.
abstract: Uroporphyrinogen decarboxylase (EC 4.1.1.37) was purified 600-fold from Rhodobacter sphaeroides grown anaerobically in the light. The enzyme, under both denaturing and non-denaturing conditions, is a monomer of M(r) 41,000. The Km values are 1.8 microM and 6.0 microM for the conversion of uroporphyrinogen I and III to coproporphyrinogen I and III respectively. The enzyme is susceptible to inhibition by both uroporphyrinogen and uroporphyrin. The pH optimum is 6.8 and the isoelectric point is 4.4. The importance of cysteine and arginine residues is implicated from studies with inhibitors. The sequence of the first 29 amino acids of the N-terminus shows a high degree of similarity to the primary structures of other uroporphyrinogen decarboxylases. Studies on the order of decarboxylation of the four acetic acid side chains of uroporphyrinogen III suggest that at high substrate levels a random route is preferred.
authors.affiliation: School of Biological Sciences, Queen Mary and Westfield College, University of London, U.K.
authors.forename: R M
authors.initials: RM
authors.lastname: Jones
authors.forename: P M
authors.initials: PM
authors.lastname: Jordan
mesh_terms: D000595:Amino Acid Sequence; D002264:Carboxylic Acids / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D004591:Electrophoresis, Polyacrylamide Gel; D006358:Hot Temperature; D007202:Indicators and Reagents; D007526:Isoelectric Point; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011166:Porphyrins / Q000494:pharmacology; D011489:Protein Denaturation; D012242:Rhodobacter sphaeroides / Q000201:enzymology*; D017386:Sequence Homology, Amino Acid; D013438:Sulfhydryl Compounds / Q000032:analysis; D014575:Uroporphyrinogen Decarboxylase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D002264:Carboxylic Acids; D007202:Indicators and Reagents; D011166:Porphyrins; D013438:Sulfhydryl Compounds; D014575:Uroporphyrinogen Decarboxylase