On the different positional specificities of peroxidation of linoleate shown by two isozymes of soybean lipoxygenase

Abstract

Summary A number of contradictory reports concerning the products of hydroperoxidation of linoleate as catalyzed by soybean lipoxygenase have appeared with claims ranging from 100% 13-hydroperoxyoctadecadienoate to 70% 13-hydroperoxyoctadecadienoate: 30% 9-hydroperoxyoctadecadienoate. Determination of the specificity of two homogeneous isozymes of soybean lipoxygenase offers a resolution of this anomaly. The first of these enzymes, the “classical” lipoxygenase originally crystallized and described by Theorell et al . (1) (lipoxygenase-1 of Christopher et al . (2)) yields only the 13-isomer. The second isozyme, lipoxygenase-2 (2), forms a 50:50 mixture of the 9- and 13-isomers.