title: Investigation of the highly active manganese superoxide dismutase from Saccharomyces cerevisiae.
abstract: Manganese superoxide dismutase (MnSOD) from different species differs in its efficiency in removing high concentrations of superoxide (O(2)(-)), due to different levels of product inhibition. Human MnSOD exhibits a substantially higher level of product inhibition than the MnSODs from bacteria. In order to investigate the mechanism of product inhibition and whether it is a feature common to eukaryotic MnSODs, we purified MnSOD from Saccharomyces cerevisiae (ScMnSOD). It was a tetramer with 0.6 equiv of Mn per monomer. The catalytic activity of ScMnSOD was investigated by pulse radiolysis and compared with human and two bacterial (Escherichia coli and Deinococcus radiodurans) MnSODs. To our surprise, ScMnSOD most efficiently facilitates removal of high concentrations of O(2)(-) among these MnSODs. The gating value k(2)/k(3) that characterizes the level of product inhibition scales as ScMnSOD > D. radiodurans MnSOD > E. coli MnSOD > human MnSOD. While most MnSODs rest as the oxidized form, ScMnSOD was isolated in the Mn(2+) oxidation state as revealed by its optical and electron paramagnetic resonance spectra. This finding poses the possibility of elucidating the origin of product inhibition by comparing human MnSOD with ScMnSOD.
authors: Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.
authors: Kevin
authors: K
authors: Barnese
authors: Yuewei
authors: Y
authors: Sheng
authors: Troy A
authors: TA
authors: Stich
authors: Edith B
authors: EB
authors: Gralla
authors: R David
authors: RD
authors: Britt
authors: Diane E
authors: DE
authors: Cabelli
authors: Joan Selverstone
authors: JS
authors: Valentine
mesh_terms: D055162:Biocatalysis; D034301:Deinococcus / Q000201:enzymology; D004926:Escherichia coli / Q000201:enzymology; D006801:Humans; D008345:Manganese / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013482:Superoxide Dismutase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008345:Manganese; D013482:Superoxide Dismutase