The Formation of threo‐11‐Hydroxy‐trans‐12: 13‐epoxy‐9‐cis‐octadecenoic Acid by Enzymic Isomerisation of 13‐l‐Hydroperoxy‐9‐cis,11‐trans‐octadecadienoic Acid by Soybean Lipoxygenase‐1

Abstract

The interaction of soybean lipoxygenase-1 with 13-l-hydroperoxy-9-cis,11-trans-octadecadienoic acid (13-hydroperoxy-linoleate), the product of the enzymic dioxygenation of linoleic acid, yields either a yellow or a purple-coloured enzyme species depending on the amount of product used. With an excess of 13-hydroperoxy-linoleate a labile purple-coloured enzyme species is formed which reverts to a yellow-coloured form with concomitant conversion of the hydroperoxy compound. In this reaction 13-hydroperoxy-linoleate isomerises into threo-11-hydroxy-trans-12: 13 epoxy-9-cis-octadecenoic acid as could be concluded from nuclear magnetic resonance and mass spectral data. Experiments with ¹³-[¹⁸O₂]hydroperoxy-linoleate showed a high retention (70%) of the two hydroperoxy oxygen atoms in the end product.