title: Heme binding and peroxidase activity of a secreted minicatalase.
abstract: Microbial pathogens often require efficient and robust H2O2scavenger activities to survive in the presence of reactive oxygen species generated by inflammatory responses. In addition to catalases and peroxidases, enzymes known to scavenge H2O2, a novel class of secreted minicatalases is found in diderm bacteria. Here, we characterize the Helicobacter pylori (Hp) minicatalase: a monomeric hemoprotein with catalase core homology. Overexpression of Hp minicatalase rescued a catalase/peroxidase-deficient Escherichia coli phenotype under aerobic conditions and limited H2O2stress. The purified enzyme lacks catalase activity, but has strong (kcat> 100 s-1) H2O2-dependent peroxidase activity toward a variety of organic substrates. Our investigations into heme binding revealed that the heme cofactor is assembled in the periplasm to form the functional holoprotein. Furthermore, we observed the presence of a disulfide bond near the heme cavity of Hp minicatalase, which is conserved in secreted minicatalases and, therefore, may play a role in heme binding.
authors.affiliation: Department of Life Sciences, University of Parma, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Mori
authors.affiliation: Department of Life Sciences, University of Parma, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Doniselli
authors.affiliation: Department of Chemistry, University of Parma, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Faroldi
authors.affiliation: Department of Life Sciences, University of Parma, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Percudani
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002374:Catalase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D015870:Gene Expression; D005816:Genetic Complementation Test; D016480:Helicobacter pylori / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D006418:Heme / Q000737:chemistry* / Q000378:metabolism; D006420:Hemeproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000494:pharmacology; D007700:Kinetics; D008958:Models, Molecular; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D019897:Periplasm / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D010544:Peroxidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D006420:Hemeproteins; D011994:Recombinant Proteins; D006418:Heme; D006861:Hydrogen Peroxide; D010544:Peroxidases; D002374:Catalase; C508532:katA protein, Helicobacter pylori
keywords: disulfide bond; heme binding; host-pathogen interaction; hydrogen peroxide; oxidative stress; periplasmic protein