title: Mutation of a critical arginine in microsomal prostaglandin E synthase-1 shifts the isomerase activity to a reductase activity that converts prostaglandin H2 into prostaglandin F2alpha.
abstract: Microsomal prostaglandin E synthase type 1 (mPGES-1) converts prostaglandin endoperoxides, generated from arachidonic acid by cyclooxygenases, into prostaglandin E2. This enzyme belongs to the membrane-associated proteins in eicosanoid and glutathione metabolism (MAPEG) family of integral membrane proteins, and because of its link to inflammatory conditions and preferential coupling to cyclooxygenase 2, it has received considerable attention as a drug target. Based on the high resolution crystal structure of human leukotriene C4 synthase, a model of mPGES-1 has been constructed in which the tripeptide co-substrate glutathione is bound in a horseshoe-shaped conformation with its thiol group positioned in close proximity to Arg-126. Mutation of Arg-126 into an Ala or Gln strongly reduces the enzyme's prostaglandin E synthase activity (85-95%), whereas mutation of a neighboring Arg-122 does not have any significant effect. Interestingly, R126A and R126Q mPGES-1 exhibit a novel, glutathione-dependent, reductase activity, which allows conversion of prostaglandin H2 into prostaglandin F2alpha. Our data show that Arg-126 is a catalytic residue in mPGES-1 and suggest that MAPEG enzymes share significant structural components of their active sites.
authors.affiliation: Department of Medical Biochemistry and Biophysics, Division of Chemistry II, Karolinska Institutet, S-171 77 Stockholm, Sweden and the Department of Molecular Biology, Swedish University of Agricultural Sciences, 751 24 Uppsala, Sweden.
authors.forename: Tove
authors.initials: T
authors.lastname: Hammarberg
authors.affiliation: Department of Medical Biochemistry and Biophysics, Division of Chemistry II, Karolinska Institutet, S-171 77 Stockholm, Sweden and the Department of Molecular Biology, Swedish University of Agricultural Sciences, 751 24 Uppsala, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Hamberg
authors.affiliation: Department of Medical Biochemistry and Biophysics, Division of Chemistry II, Karolinska Institutet, S-171 77 Stockholm, Sweden and the Department of Molecular Biology, Swedish University of Agricultural Sciences, 751 24 Uppsala, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Wetterholm
authors.affiliation: Department of Medical Biochemistry and Biophysics, Division of Chemistry II, Karolinska Institutet, S-171 77 Stockholm, Sweden and the Department of Molecular Biology, Swedish University of Agricultural Sciences, 751 24 Uppsala, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Hansson
authors.affiliation: Department of Medical Biochemistry and Biophysics, Division of Chemistry II, Karolinska Institutet, S-171 77 Stockholm, Sweden and the Department of Molecular Biology, Swedish University of Agricultural Sciences, 751 24 Uppsala, Sweden.
authors.forename: Bengt
authors.initials: B
authors.lastname: Samuelsson
authors.affiliation: Department of Medical Biochemistry and Biophysics, Division of Chemistry II, Karolinska Institutet, S-171 77 Stockholm, Sweden and the Department of Molecular Biology, Swedish University of Agricultural Sciences, 751 24 Uppsala, Sweden. Electronic address: jesper.haeggstrom@ki.se.
authors.forename: Jesper Z
authors.initials: JZ
authors.lastname: Haeggstro M
mesh_terms: D019943:Amino Acid Substitution; D001120:Arginine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D015237:Dinoprost / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology*; D008958:Models, Molecular; D020125:Mutation, Missense; D010088:Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D044262:Prostaglandin H2 / Q000737:chemistry* / Q000378:metabolism; D000071876:Prostaglandin-E Synthases; D017434:Protein Structure, Tertiary / Q000235:genetics; D040681:Structural Homology, Protein; D013329:Structure-Activity Relationship
chemical_list: D044262:Prostaglandin H2; D001120:Arginine; D015237:Dinoprost; D010088:Oxidoreductases; D019746:Intramolecular Oxidoreductases; C000605862:PTGES protein, human; D000071876:Prostaglandin-E Synthases