Enzymatically-derived PGE
2 is an optically pure compound whereas PGE
2 derived from the free radical-catalyzed peroxidation of arachidonate is a racemic mixture.
Ent-PGE
2 is the opposite enantiomer of PGE
2. Significant amounts of racemic PGE
2 (
rac-PGE
2) are generated
in vitro and
in vivo in settings of oxidative stress
via the isoprostane pathway. A proposed mechanism for the formation of
rac-PGE
2 involves the base catalyzed equilibration from 15-E
2t-isoprostane (8-
iso-PGE
2), generated from the 15-H
2t-
isoprostane endoperoxide.
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