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Prostaglandin E Synthase, a Terminal Enzyme for Prostaglandin E<sup>2</sup> Biosynthesis
Kudo, Ichiro,Murakami, Makoto Korean Society for Biochemistry and Molecular Biol 2005 Journal of biochemistry and molecular biology Vol.38 No.6
Biosynthesis of prostanoids is regulated by three sequential enzymatic steps, namely phospholipase $A_2$ enzymes, cyclooxygenase (COX) enzymes, and various lineage-specific terminal prostanoid synthases. Prostaglandin E synthase (PGES), which isomerizes COX-derived $PGH_2$ specifically to $PGE_2$, occurs in multiple forms with distinct enzymatic properties, expressions, localizations and functions. Two of them are membrane-bound enzymes and have been designated as mPGES-1 and mPGES-2. mPGES-1 is a perinuclear protein that is markedly induced by proinflammatory stimuli, is down-regulated by anti inflammatory glucocorticoids, and is functionally coupled with COX-2 in marked preference to COX-1. Recent gene targeting studies of mPGES-1 have revealed that this enzyme represents a novel target for anti-inflammatory and anti-cancer drugs. mPGES-2 is synthesized as a Golgi membrane-associated protein, and the proteolytic removal of the N-terminal hydrophobic domain leads to the formation of a mature cytosolic enzyme. This enzyme is rather constitutively expressed in various cells and tissues and is functionally coupled with both COX-1 and COX-2. Cytosolic PGES (cPGES) is constitutively expressed in a wide variety of cells and is functionally linked to COX-1 to promote immediate $PGE_2$ production. This review highlights the latest understanding of the expression, regulation and functions of these three PGES enzymes.
Proteinaceous inhibitors of phospholipase A₂ purified from inflammatory sites in rats
SUWA, YORIMAS,KUDO, ICHIRO,IMAIZUMI, ATSUSHI,OKADA, MASAHIRO,KAMIMURA, TAKASHI,SUZUKI, YOJI,CHANG, HYEUN WOOK,HARA, SHUNTARO,INOUE, KEIZO 영남대학교 약품개발연구소 1991 영남대학교 약품개발연구소 연구업적집 Vol.1 No.-
We have purified two phospholipase A₂ inhibitory proteins (37 and 33 kDa) from peritoneal fluid of dexamethasone-treated rats. The extracellular phospholipase A₂ round in inflammatory sites differed from the exocrine phospholipase A₂ in susceptibility to these endogenous inhibitors; both proteins inhibited the activity of the extracellular phospholipase A₂ purified from sites of inflammation but did not affect appreciably the activity of either porcine pancreatic or Naja naja venom phospholipase A₂. The amino acid sequence of the NH₂-terminal portion of the purified proteins did not resemble that of lipocortins so far reported, but it was almost identical to that of parts of human or mouse complement component C3. These findings may indicate that degraded products of C3 are involved in the regulation of activity of a class of mammalian phospholipase A₂.
Moon, Tae Chul,Murakami, Makoto,Ashraf, MD Musharaf,Kudo, Ichiro,Chang, Hyeun Wook 영남대학교 약품개발연구소 1998 영남대학교 약품개발연구소 연구업적집 Vol.8 No.-
Emerging evidence has suggested the pivotal role of mast cells in a host defense against bacterial infection. In this paper, we report that bacterial lipopolysaccharide (LPS) is a potent enhancer of the cytokine- and IgE-dependent delayed responses of IL-3-dependent mouse bone marrow-derived cultured mast cells (BMMC). LPS, although showing minimal effects, significantly augmented the c-kit ligand (KL)- or IgE-dependent expression of cyclooxygenase (COX)-2 and the attendant delayed PGD₂ generation, with IL-10 and IL-4 acting as potentiating and inhibitory cytokines, respectively. The COX-2-inducing activity of LPS was mimicked by exogenous IL-1β. Assessment Of endogenous cytokine induction revealed that IL-1β expression was stimulated by either LPS or exogenous IL-1β. IL-6 expression occurred in parallel with COX-2 expression. IL-10 expression, which lagged behind COX-2 expression, depended on exogenous IL-10, but not on LPS and IL-1β. Thus, LPS and IL-1β exhibited similar biological activities in terms of COX-2 and endogenous cytokine expression. However, adding an antibody against the type I IL-1 receptor to BMMC, which abrogated the effects of IL-1β, failed to neutralize the effects of LPS. These results suggest that LPS activates BMMC through the signal transduction pathway shared with exogenous IL-1β, rather than exerting its action indirectly via the production of endogenous IL-1β. ⓒ 1998 Academic Press