Dioxygenase and peroxidase activities of soybean lipoxygenase: synergistic interaction between linoleic acid and hydrogen peroxide.

The interaction of H2O2 with soyabean lipoxygenase was investigated in the presence of linoleic acid. Dioxygenase activity was significantly higher at pH 9.0 than at pH 6.0. H2O2 at concentrations less than 1.0 nM stimulated linoleic acid oxidation synergistically and the magnitude of synergism was higher at pH 9.0. Linoleic acid dependent peroxidase activity towards benzidine, guaiacol, tetramethylbenzidine (TMBD) and tetramethylphenylenediamine (TMPD) was higher at pH 9.0, whereas pyrogallol and ABTS oxidation rates were higher at pH 6.0. H2O2 supported oxidation of benzidine, guaiacol, pyrogallol and ABTS was higher at pH 6.0, whereas TMPD, TMBD exhibited higher oxidation rates at pH 9.0. H2O2 in the presence of linoleic acid produced synergism in xenobotic metabolism and depending upon the substrate in question upto 11-fold increase in oxidation rate was noted.