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J Biol Chem. 2000 Oct 20;275(42):32775-82.

Molecular identification of cytosolic prostaglandin E2 synthase that is functionally coupled with cyclooxygenase-1 in immediate prostaglandin E2 biosynthesis.

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  • 1Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142, Japan.

Abstract

Here we report the molecular identification of cytosolic glutathione (GSH)-dependent prostaglandin (PG) E(2) synthase (cPGES), a terminal enzyme of the cyclooxygenase (COX)-1-mediated PGE(2) biosynthetic pathway. GSH-dependent PGES activity in the cytosol of rat brains, but not of other tissues, increased 3-fold after lipopolysaccharide (LPS) challenge. Peptide microsequencing of purified enzyme revealed that it was identical to p23, which is reportedly the weakly bound component of the steroid hormone receptor/hsp90 complex. Recombinant p23 expressed in Escherichia coli and 293 cells exhibited all the features of PGES activity detected in rat brain cytosol. A tyrosine residue near the N terminus (Tyr(9)), which is known to be critical for the activity of cytosolic GSH S-transferases, was essential for PGES activity. The expression of cPGES/p23 was constitutive and was unaltered by proinflammatory stimuli in various cells and tissues, except that it was increased significantly in rat brain after LPS treatment. cPGES/p23 was functionally linked with COX-1 in marked preference to COX-2 to produce PGE(2) from exogenous and endogenous arachidonic acid, the latter being supplied by cytosolic phospholipase A(2) in the immediate response. Thus, functional coupling between COX-1 and cPGES/p23 may contribute to production of the PGE(2) that plays a role in maintenance of tissue homeostasis.

PMID:
10922363
[PubMed - indexed for MEDLINE]
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