Prostaglandin H Synthase-2-catalyzed Oxygenation of 2-Arachidonoylglycerol Is More Sensitive to Peroxide Tone than Oxygenation of Arachidonic Acid

Vanderbilt University, Нашвилл, Michigan, United States
Journal of Biological Chemistry (Impact Factor: 4.57). 09/2012; 287(44). DOI: 10.1074/jbc.M112.381202
Source: PubMed


The endocannabinoid, 2-arachidonoylglycerol (2-AG), is a selective substrate for the inducible isoform of prostaglandin H
synthase (PGHS), PGHS-2. Its turnover leads to the formation of glyceryl esters of prostaglandins (PG-Gs), a subset of which
elicits agonism at unique, as yet unidentified, receptors. The kcat/Km values for oxygenation of arachidonic acid (AA) and 2-AG by PGHS-2 are very similar, but the sensitivities of the two substrates
to peroxide-dependent activation have not been compared. 15-Hydroperoxy derivatives of AA and 2-AG were found to be comparable
in their ability to serve as substrates for the peroxidase activities of PGHS-2, PGHS-1, and glutathione peroxidase (GPx).
They also were comparable in the activation of AA oxygenation by cyanide-inhibited PGHS-2. However, oxygenation of 2-AG was
significantly suppressed relative to AA by the presence of GPx and GSH. Furthermore, 2-AG oxygenation by peroxidase-deficient
H388YmPGHS-2 was much less efficient than AA oxygenation. Wild-type rates of 2-AG oxygenation were restored by treatment of
H388YmPGHS-2 with hydroperoxide derivatives of AA or 2-AG. RNAi silencing of phospholipid hydroperoxide-specific GPx (GPx4)
in NIH/3T3 cells led to increases in cellular peroxidation and in the levels of the isoprostane product, 8-epi-PGF2α. GPx4 silencing led to 2–4-fold increases in PG-G formation but no change in PG formation. Thus, cellular peroxide tone may
be an important determinant of the extent of endocannabinoid oxygenation by PGHS-2.

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    • "Vertebrates have two distinct PGHS isoforms: PGHS-1 and -2 (Kulmacz et al. 2003; Rouzer and Marnett 2009; Simmons et al. 2004; Smith et al. 2000b). The majority of the studies associated with mammalian PGHSs have been conducted with native or recombinant ovine PGHS-1 and recombinant human or murine PGHS-2 (Mbonye et al. 2006; Musee and Marnett 2012; Nemeth et al. 2001; Vecchio and Malkowski 2011; Vecchio et al. 2012). Thus there is little experimental data on human PGHSs (hPGHSs), particularly concerning hPGHS-1. "
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