The Formation of <i>threo</i>‐11‐Hydroxy‐<i>trans</i>‐12: 13‐epoxy‐9‐<i>cis</i>‐octadecenoic Acid by Enzymic Isomerisation of 13‐<scp>l</scp>‐Hydroperoxy‐9‐<i>cis</i>,11‐<i>trans</i>‐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 2 hydroperoxy oxygen atoms in the end product.