title: Interaction of nitric oxide with catalase: structural and kinetic analysis.
abstract: We present the structures of bovine catalase in its native form and complexed with ammonia and nitric oxide, obtained by X-ray crystallography. Using the NO generator 1-(N,N-diethylamino)diazen-1-ium-1,2-diolate, we were able to generate sufficiently high NO concentrations within the catalase crystals that substantial occupation was observed despite a high dissociation rate. Nitric oxide seems to be slightly bent from the heme normal that may indicate some iron(II) character in the formally ferric catalase. Microspectrophotometric investigations inline with the synchrotron X-ray beam reveal photoreduction of the central heme iron. In the cases of the native and ammonia-complexed catalase, reduction is accompanied by a relaxation phase. This is likely not the case for the catalase NO complex. The kinetics of binding of NO to catalase were investigated using NO photolyzed from N,N'-bis(carboxymethyl)-N,N'-dinitroso-p-phenylenediamine using an assay that combines catalase with myoglobin binding kinetics. The off rate is 1.5 s(-1). Implications for catalase function are discussed.
authors.affiliation: Department of Physics, University of Wisconsin-Milwaukee, 1900 East Kenwood Boulevard, Milwaukee, WI 53211, USA.
authors.forename: Namrta
authors.initials: N
authors.lastname: Purwar
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: McGarry
authors.forename: Joshua
authors.initials: J
authors.lastname: Kostera
authors.forename: A Andrew
authors.initials: AA
authors.lastname: Pacheco
authors.forename: Marius
authors.initials: M
authors.lastname: Schmidt
mesh_terms: D000818:Animals; D002374:Catalase / Q000737:chemistry / Q000378:metabolism*; D002417:Cattle; D018360:Crystallography, X-Ray; D007700:Kinetics; D009569:Nitric Oxide / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation
chemical_list: D009569:Nitric Oxide; D002374:Catalase