title: Nucleotide sequence analysis, overexpression in Escherichia coli and kinetic characterization of Anacystis nidulans catalase-peroxidase.
abstract: Bifunctional catalase-peroxidases are the least understood type of peroxidases. A high-level expression in Escherichia coli of a fully active recombinant form of a catalase-peroxidase (KatG) from the cyanobacterium Anacystis nidulans (Synechococcus PCC 6301) is reported. Since both physical and kinetic characterization revealed its identity with the wild-type protein, the large quantities of recombinant KatG allowed the examination of both the spectral characteristics and the reactivity of its redox intermediates by using the multi-mixing stopped-flow technique. The homodimeric acidic protein (pI = 4.6) contained high catalase activity (apparent K(m) = 4.8 mM and apparent k(cat) = 8850 s(-1)). Cyanide is shown to be an effective inhibitor of the catalase reaction. The second-order rate constant for cyanide binding to the ferric protein is (6.9 +/- 0.2) x 10(5) M(-1 )s(-1) at pH 7.0 and 15 degrees C and the dissociation constant of the cyanide complex is 17 microM. Because of the overwhelming catalase activity, peroxoacetic acid has been used for compound I formation. The apparent second-order rate constant for formation of compound I from the ferric enzyme and peroxoacetic acid is (1.3 +/- 0.3) x 10(4 )M(-1 )s(-1) at pH 7.0 and 15 degrees C. The spectrum of compound I is characterized by about 40% hypochromicity, a Soret region at 406 nm, and isosbestic points between the native enzyme and compound I at 355 and 428 nm. Rate constants for reduction of KatG compound I by o-dianisidine, pyrogallol, aniline and isoniazid are shown to be (7.3 +/- 0.4) x 10(6) M(-1 )s(-1), (5.4 +/- 0.3) x 10(5) M(-1 )s(-1), (1.6 +/- 0.3) x 10(5) M(-1 )s(-1) and (4.3 +/- 0.2) x 10(4) M(-1 )s(-1), respectively. The redox intermediate formed upon reduction of compound I did not exhibit the classical red-shifted peroxidase compound II spectrum which characterizes the presence of a ferryl oxygen species. Its spectral features indicate that the single oxidizing equivalent in KatG compound II is contained on an amino acid which is not electronically coupled to the heme.
authors.affiliation: Institute of Chemistry, University of Agricultural Sciences, Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Engleder
authors.forename: G
authors.initials: G
authors.lastname: Regelsberger
authors.forename: C
authors.initials: C
authors.lastname: Jakopitsch
authors.forename: P G
authors.initials: PG
authors.lastname: Furtmüller
authors.forename: F
authors.initials: F
authors.lastname: Rüker
authors.forename: G A
authors.initials: GA
authors.lastname: Peschek
authors.forename: C
authors.initials: C
authors.lastname: Obinger
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D002384:Catalysis; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000201:enzymology* / Q000235:genetics; D017931:DNA Primers; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000235:genetics; D007700:Kinetics; D008024:Ligands; D008969:Molecular Sequence Data; D010544:Peroxidases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013057:Spectrum Analysis
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D008024:Ligands; D011994:Recombinant Proteins; D010544:Peroxidases; C076136:catalase HPI