A study of oxygen isotope scrambling in the enzymic and non-enzymic oxidation of linoleic acid.

Lipoxygenases-1 and -2 isolated from soybeans were incubated with linoleic acid in the presence of a mixture of 16O2 and 18O2. The formation of 16O/18O-molecules which is indicative for a head-to head reaction of peroxy radicals was determined and compared with that produced during autoxidation of a linoleic acid emulsion in the presence of ferric ions. Lipoxygenase-1 was much less active in scrambling than lipoxygenase-2 which was comparable to that found in the autoxidation reaction.