title: Analyses of methionine sulfoxide reductase activities towards free and peptidyl methionine sulfoxides.
abstract: There have been insufficient kinetic data that enable a direct comparison between free and peptide methionine sulfoxide reductase activities of either MsrB or MsrA. In this study, we determined the kinetic parameters of mammalian and yeast MsrBs and MsrAs for the reduction of both free methionine sulfoxide (Met-O) and peptidyl Met-O under the same assay conditions. Catalytic efficiency of mammalian and yeast MsrBs towards free Met-O was >2000-fold lower than that of yeast fRMsr, which is specific for free Met-R-O. The ratio of free to peptide Msr activity in MsrBs was 1:20-40. In contrast, mammalian and yeast MsrAs reduced free Met-O much more efficiently than MsrBs. Their k(cat) values were 40-500-fold greater than those of the corresponding MsrBs. The ratio of free to peptide Msr activity was 1:0.8 in yeast MsrA, indicating that this enzyme can reduce free Met-O as efficiently as peptidyl Met-O. In addition, we analyzed the in vivo free Msr activities of MsrBs and MsrAs in yeast cells using a growth complementation assay. Mammalian and yeast MsrBs, as well as the corresponding MsrAs, had apparent in vivo free Msr activities. The in vivo free Msr activities of MsrBs and MsrAs agreed with their in vitro activities.
authors.affiliation: Department of Biochemistry and Molecular Biology, Yeungnam University College of Medicine, Daegu 705-717, Republic of Korea.
authors.forename: Geun-Hee
authors.initials: GH
authors.lastname: Kwak
authors.forename: Kwang Yeon
authors.initials: KY
authors.lastname: Hwang
authors.forename: Hwa-Young
authors.initials: HY
authors.lastname: Kim
mesh_terms: D000818:Animals; D017353:Gene Deletion; D006801:Humans; D007700:Kinetics; D008715:Methionine / Q000031:analogs & derivatives* / Q000378:metabolism; D051150:Methionine Sulfoxide Reductases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010084:Oxidation-Reduction; D010455:Peptides / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D010455:Peptides; D029701:Saccharomyces cerevisiae Proteins; D008715:Methionine; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase; C013111:methionine sulfoxide