Comparison of the Substrate Specificities of Lipoxygenases Purified from Soybean Seed, Wheat Seed, and Cucumber Cotyledons

Abstract

Abstract Lipoxygenases were highly purified from soybean seed, wheat seed and cucumber cotyledons. Substrate specificities of these lipoxygenases were studied by using an entire series of (ω6Z ,ω9Z )-C13~C24-dienoic acids as synthetic substrate analogues. Soybean lipoxygenase-1 and cucumber lipoxygenase showed broad specificities for these substrates while wheat lipoxygenase showed narrow specificities. Position of dioxygenation to each substrate was analyzed by high performance liquid chromatography. With soybean lipoxygenase-1 elongation of the distance between the terminal carboxyl group and the site of hydrogen removal in a substrate decreased the positional specificity of dioxygenation, while, with cucumber lipoxygenase, shortening the distance decreased the specificity. It was suggested that cucumber lipoxygenase and soybean lipoxygenase-1 recognized the terminal carboxyl group of a substrate to arrange it only in one orientation at the reaction center. In case of wheat lipoxygenase, recognition of the carboxyl group was thought to have crucial and essential role to secure the activity.