Enzyme lipoxygenase , activity

PGH synthase and the related enzyme lipoxygenase occupy a position at the interface of peroxidase chemistry and free radical chemistry and can clearly trigger metabolic activation by both mechanisms. The peroxidase pathway activates compounds such as diethylstilbestrol and aromatic amines whereas the free radical pathway activates polycyclic hydrocarbons (59). Both pathways require synthesis of hydroperoxide in order to trigger oxidation. 

Shimizu T, Radmark O, Samuelsson B (1984) Enzyme with dual lipoxygenase activities catalyzes leukotriene A4 synthesis from arachidonic acid. Proc Natl Acad Sci USA... 

Isoenzymes. Kies (90), who questioned the identity of lipoxygenase and carotene oxidase, thought that the lipoxygenase activity of soybeans was caused by more than one enzyme. She discovered that a partially... 

Effects on antioxidant enzymes. Along with anti-radical effects camosine can influence enzymes which activity is connected directly or indirectly to free radical metabolism. Camosine and other CRC may work as NO synthase inhibitors in muscles [54]. Low concentrations of camosine (until 2.5 mM) can activate rabbit platelets 5 -lipoxygenase, whereas higher concentrations inhibit it [55]. Camosine, homocamosine or anserine (15-25 pM) inhibit rat brain tirosine hydroxylase by 50% at very low concentrations [56]. It was demonstrated recently that camosine may protect SOD from ROS attack under in vitro [57], and in vivo (our unpublished data) oxidative stress. 

The mechanisms of action of ketoprofen have not been definitively proven in the horse, although ketoprofen has been shown to inhibit COX enzymes. Several studies carried out in horses have shown that ketoprofen, administered at doses that significantly inhibited PG production, had no effect on LT production (Landoni Lees 1995a, Owens et al 1995a) and, therefore, appears not to have any significant effect on lipoxygenase activity. 

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