Mediated Reactions and Related Mediators

Aspirin acetylates a serine residue positioned in the catalytic site of the enzyme (Ser529 of COX-1 and Ser516 of COX-2) resulting in irreversible inhibition of COX-1/2 (Loll et al. 1995). However, the acetylated-COX-2 (ac-COX-2) retains part of its catalytic activity and can still act as a peroxidase forming R monohydroxy fatty acids such as 15R-HETE from AA, 18R-HEPE from EPA and 17/ -HDHA (Mancini et al. 1994 Serhan et al. 2008 Sharma et al. 2010). 

Although the COX reaction requires catalytic levels of peroxide, the enzyme activity is not directly affected by ROS production (Smith 2008). However, ROS-mediated increase of the inducible enzymes involved in the arachidonic acid cascade, including phospholipases that provide free AA and other PUFA substrates for COX-mediated reactions, COX-2 and prostaglandin synthases (see Section 3.1), makes the formation of eicosanoids sensitive to the cellular redox status, and this can impact on disease states characterized by oxidative stress (Korbecki et al. 2013). 

Prostaglandin E synthase (PGES) catalyzes the isomerization of PGH to PGE. Three types of PGES have been characterized the cytosolic PGES (cPGES) and 

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