title: The structure and peroxidase activity of a 33-kDa catalase-related protein from Mycobacterium avium ssp. paratuberculosis.
abstract: True catalases are tyrosine-liganded, usually tetrameric, hemoproteins with subunit sizes of approximately 55-84 kDa. Recently characterized hemoproteins with a catalase-related structure, yet lacking in catalatic activity, include the 40-43 kDa allene oxide synthases of marine invertebrates and cyanobacteria. Herein, we describe the 1.8 A X-ray crystal structure of a 33 kDa subunit hemoprotein from Mycobacterium avium ssp. paratuberculosis (annotated as MAP-2744c), that retains the core elements of the catalase fold and exhibits an organic peroxide-dependent peroxidase activity. MAP-2744c exhibits negligible catalatic activity, weak peroxidatic activity using hydrogen peroxide (20/s) and strong peroxidase activity (approximately 300/s) using organic hydroperoxides as co-substrate. Key amino acid differences significantly impact prosthetic group conformation and placement and confer a distinct activity to this prototypical member of a group of conserved bacterial "minicatalases". Its structural features and the result of the enzyme assays support a role for MAP-2744c and its close homologues in mitigating challenge by a variety of reactive oxygen species.
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Pakhomova
authors.forename: Benlian
authors.initials: B
authors.lastname: Gao
authors.forename: William E
authors.initials: WE
authors.lastname: Boeglin
authors.forename: Alan R
authors.initials: AR
authors.lastname: Brash
authors.forename: Marcia E
authors.initials: ME
authors.lastname: Newcomer
mesh_terms: D000595:Amino Acid Sequence; D002374:Catalase / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D006418:Heme / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016927:Mycobacterium avium subsp. paratuberculosis / Q000201:enzymology*; D009195:Peroxidase / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation
chemical_list: D006418:Heme; D002374:Catalase; D009195:Peroxidase