title: The homopentameric chlorite dismutase from Magnetospirillum sp.
abstract: Chlorite dismutase (Cld) is a b-type heme containing enzyme that catalyzes the reduction of chlorite into chloride plus dioxygen. This enzyme has gained attention because it can be used in the development of bioremediation processes, biosensors, and controlled dioxygen production. In the present work, Cld was purified from Magnetospirillum sp. cells cultured anaerobically with acetate/perchlorate until stationary phase. Biochemical, spectroscopic and X-ray crystallography methods showed that Cld from Magnetospirillum sp. is a ~140 kDa homopentamer comprising ~27.8 kDa monomers. Preliminary X-ray crystallography studies confirmed the quaternary structure and the presence of one b-type heme per monomer. The EPR spectroscopic signature of the as-purified Cld samples is affected by the buffer composition used during the purification. Potassium phosphate buffer is the only buffer that affected neither the spectral nor the kinetic properties of Cld. Kinetic studies in solution revealed that Cld from Magnetospirillum sp. decomposes chlorite at high turnover rates with optimal pH6.0. A temperature below 10 °C is required to avoid enzyme inactivation due to cofactor bleaching during turnover, and to achieve full substrate consumption. Cld kinetic parameters were not affected when kinetic assays were performed in the presence of air or under argon atmosphere, but chloride is a weak mixed inhibitor that modifies the EPR signal of as-prepared samples.
authors.affiliation: UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors.forename: Diana M
authors.initials: DM
authors.lastname: Freire
authors.affiliation: UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal; Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, S3000ZAA Santa Fe, Argentina.
authors.forename: Maria G
authors.initials: MG
authors.lastname: Rivas
authors.affiliation: UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors.forename: André M
authors.initials: AM
authors.lastname: Dias
authors.affiliation: UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors.forename: Ana T
authors.initials: AT
authors.lastname: Lopes
authors.affiliation: UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors.forename: Cristina
authors.initials: C
authors.lastname: Costa
authors.affiliation: UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors.forename: Teresa
authors.initials: T
authors.lastname: Santos-Silva
authors.affiliation: Department of Physics, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium. Electronic address: sabine.vandoorslaer@ua.ac.be.
authors.forename: Sabine
authors.initials: S
authors.lastname: Van Doorslaer
authors.affiliation: UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal; Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje El Pozo, S3000ZAA Santa Fe, Argentina. Electronic address: pgonzalez@fbcb.unl.edu.ar.
authors.forename: Pablo J
authors.initials: PJ
authors.lastname: González
mesh_terms: D018360:Crystallography, X-Ray; D004591:Electrophoresis, Polyacrylamide Gel; D006418:Heme / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D042201:Magnetospirillum / Q000201:enzymology*; D008958:Models, Molecular; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013696:Temperature
chemical_list: D006418:Heme; D010088:Oxidoreductases; C402794:chlorite dismutase
keywords: Chlorite dismutase; EPR spectroscopy; Enzyme kinetics; Magnetospirillum; Perchlorate-reducing bacteria; X-ray crystallography