Dimorphotheca sinuata lipoxygenase: formation of 13-L-hydroperoxy-cis-9,trans- 11-octadecadienoic acid from linoleic acid.

Abstract

AbstractLipoxygenase (EC 1.13.1.13) from the seed ofDimorphotheca sinuata oxidized linoleic acid to predominantly 13‐L‐hydroperoxy‐cis‐9,trans‐11‐octadecadienoic acid. When the reaction proceeded at pH 6.9, the 13‐hydroperoxide was the only isomer detected; but at pH 5.1, the 13‐isomer was 92% of the total, the remaining 8% being the 9‐hydroperoxide. At both pH's small amounts of hydroxyoctadecadienoic acid accumulated during the reaction. This acid from the pH 6.9 reaction was analyzed as 13‐hydroxy‐cis,trans‐octadecadienoic. The postulate advanced by many workers that dimorphecolic acid, 9‐D‐hydroxy‐trans‐10,trans‐12‐octadecadienoic acid, is biosynthesized via a lipoxygenase product was not proved. Although the product specificity ofD. sinuata lipoxygenase is like that of lipoxygenase type 1 from soybeans, its inactivity at pH 9 demonstrated that it is a novel enzyme.