Characterization of metabolic pathway of linoleic acid 9-hydroperoxide in cytosolic fraction of potato tubers and identification of reaction products |
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Authors: | Hideto Kimura Kazushige Yokota |
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Institution: | (1) Department of Life Science and Biotechnology, Shimane University, 1060 Nishikawatsu-cho, Matsue, 690-8504 Shimane, Japan |
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Abstract: | Potato tubers are shown to contain a unique lipoxygenase pathway to form 9-hydroperoxy-10,12-octadecadienoic acid (9-HPODE)
from linoleic acid. Here, we report the metabolic pathway of 9-HPODE in the cytosolic fraction and the characterization of
enzymes involved in the conversion of metabolites. The analysis of enzymatic reaction products at pH 5.5 revealed the formation
of 9-keto-10,12-octadecadienoic acid, 9-hydroxy-10,12-octadecadienoic acid, 9,10-epoxy-11-hydroxy-12-octadecenoic acid, 9,10,13-trihydroxy-11-octadecenoic
acid, and 9,12,13-trihydroxy-10-octadecenoic acid. The cytosolic enzymes were separated by anion-exchange chromatography into
two fractions E1 and E2, having molecular masses of 66 and 54 kDa, respectively. The enzyme fraction E1 only produced 9-keto-10,12-octadecadienoic
acid, whereas E2 formed other products. The enzyme E1 showed higher reactivity with 13- and 9-hydroperoxide of α-linolenic
acid than 9-HPODE, but no reaction with hydroxy fatty acids. In contrast, the enzyme E2 showed the highest reactivity with
9-HPODE, followed by hydroperoxides of α-linolenic acid and arachidonic acid. We also evaluated the antibacterial activity
of hydroxy fatty acids against Erwinia carotovora T-29, a bacterium infecting potato tubers. Growth of the bacteria was suppressed more potently with 9- or 13-hydroxy fatty
acids than dihydroxy or trihydroxy fatty acids, suggesting a role for the metabolites in the resistance of bacterial infection. |
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Keywords: | Potato tuber linoleic acid 9-hydroperoxide hydroxy fatty acids Erwinia carotovora T-29 bacterial infection |
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