title: Purification and properties of porphobilinogen deaminase from Arabidopsis thaliana.
abstract: Porphobilinogen deaminase (EC 4.3.1.8) has been purified to homogeneity (16,000-fold) from the plant Arabidopsis thaliana in yields of 8%. The deaminase is a monomer of M(r) 35,000, as shown by SDS/PAGE, and 31,000, using gel-filtration chromatography. The pure enzyme has a Vmax. of 4.5 mumol/h per mg and a Km of 17 +/- 4 microM. Determination of the pI and pH optimum revealed values of 5.2 and 8.0 respectively. The sequence of the N-terminus was found to be NH2-XVAVEQKTRTAI. The deaminase is heat-stable up to 70 degrees C and is inhibited by NH3 and hydroxylamine. The enzyme is inactivated by arginine-, histidine- and lysine-specific reagents. Incubation with the substrate analogue and suicide inhibitor, 2-bromoporphobilinogen, results in chain termination and in inactivation.
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; D000641:Ammonia / Q000494:pharmacology; D017360:Arabidopsis / Q000201:enzymology*; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D019811:Hydroxylamine; D006898:Hydroxylamines / Q000494:pharmacology; D011163:Hydroxymethylbilane Synthase / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D007526:Isoelectric Point; D007700:Kinetics; D008670:Metals / Q000494:pharmacology; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011162:Porphobilinogen / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology
chemical_list: D006898:Hydroxylamines; D008670:Metals; C058806:2-bromoporphobilinogen; C056776:dipyrromethane cofactor; D019811:Hydroxylamine; D011162:Porphobilinogen; D000641:Ammonia; D011163:Hydroxymethylbilane Synthase