Decomposition of lipid hydroperoxide by soybean lipoxygenase-1 under aerobic conditions studied by high performance liquid chromatography and the spin trapping method.

Abstract

The decomposition of lipid hydroperoxide by soybean lipoxygenase-1 (EC 1.13.11.12) under aerobic conditions was studied by high performance liquid chromatography and the spin trapping method. The reaction followed first order kinetics for lipid hydroperoxide. Its rate was proportional to the enzyme concentration and was independent of pH. A decrease in reactivity due to thermal denaturation and H202-modification of the enzyme indicated that native lipoxygenase was involved in the decomposition of the lipid hydroperoxide. The free radical, possibly the alkyl radical, was trapped by a radical scavenger, 2-methyl-2-nitrosopropane, in the mixture of soybean lipoxygenase-1 and the lipid hydroperoxide. These results indicated a free-radical chain reaction mechanism for decompositon of the lipid hydroperoxide initiated by soybean lipoxygenase-1.