title: Studies on membrane-associated prostaglandin E synthase-2 with reference to production of 12L-hydroxy-5,8,10-heptadecatrienoic acid (HHT).
abstract: Membrane-associated prostaglandin (PG) E synthase (mPGE synthase)-2 catalyzes the conversion of PGH(2) primarily to PGE(2). The enzyme is activated by various sulfhydryl reagents including dithiothreitol, dihydrolipoic acid, and glutathione, and it is different from mPGE synthase-1 and cytosolic PGE synthase, both of which require specifically glutathione. Recently, other investigators reported that their preparation of mPGE synthase-2 containing heme converted PGH(2) to 12L-hydroxy-5,8,10-heptadecatrienoic acid (HHT) rather than to PGE(2) [T. Yamada, F. Takusagawa, Biochemistry 46 (2007) 8414-8424]. As we examined presently, the heme-bound enzyme expressed and purified according to their method synthesized HHT from PGH(2), but also PGE(2) in a decreased amount. Whereas the PGE synthase activity was completely lost at 50 degrees C for 5 min, the HHT synthase activity remained even at 100 degrees C for 5 min. In contrast, when the heme-bound enzyme was purified in the presence of dithiothreitol, only PGE(2) was produced, but essentially no HHT was detected. Thus, native mPGE synthase-2 enzymatically catalyzes only the conversion of PGH(2) to PGE(2), but not to HHT, and heme is not involved in this reaction.
authors.affiliation: Division of Life Science, Graduate School of Integrated Science and Art, University of East Asia, 2-1 Ichinomiyagakuen, Shimonoseki, Yamaguchi 751-8503, Japan.
authors.forename: Kikuko
authors.initials: K
authors.lastname: Watanabe
authors.forename: Seiji
authors.initials: S
authors.lastname: Ito
authors.forename: Shozo
authors.initials: S
authors.lastname: Yamamoto
mesh_terms: D002462:Cell Membrane / Q000378:metabolism*; D004229:Dithiothreitol / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D006248:Harringtonines / Q000378:metabolism*; D019746:Intramolecular Oxidoreductases / Q000378:metabolism*; D000071876:Prostaglandin-E Synthases; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: C481002:2'-hydroxy-2'-(alpha-acetic acid)-6'-hydroxy-6'-methylheptanoyl cephalotaxine; D006248:Harringtonines; D011994:Recombinant Proteins; D019746:Intramolecular Oxidoreductases; D000071876:Prostaglandin-E Synthases; D004229:Dithiothreitol