15-LOX type 1 is the initiating enzyme in the RCTR pathway which catalyzes the formation of 17S-hydro(peroxy)-4Z,7Z,10Z,13Z,15E,19Z-docosahexaenoic acid via subsequent lipoxygenase activity this substrate is converted to 7, 8-epoxy, 17S-hydroxy-4Z,9,11,13,15,19Z-docosahexaenoic acid that is precursor to RCTR1. This mediator is converted to RCTR2 that in turn produces RCTR3.