Characterization of metabolic pathway of linoleic acid 9-hydroperoxide in cytosolic fraction of potato tubers and identification of reaction products.
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 alpha-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 alpha-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.
Kimura
Hideto
H
Department of Life Science and Biotechnology, Shimane University, 1060 Nishikawatsu-cho, Matsue, 690-8504, Japan.
Yokota
Kazushige
K
D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D003600:Cytosol / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006880:Hydroxy Acids / Q000378:metabolism; D008041:Linoleic Acids / Q000378:metabolism*; D008054:Lipid Peroxides / Q000378:metabolism*; D013058:Mass Spectrometry; D016973:Pectobacterium carotovorum / Q000378:metabolism / Q000472:pathogenicity; D035281:Plant Tubers / Q000201:enzymology / Q000378:metabolism*; D011198:Solanum tuberosum / Q000201:enzymology / Q000378:metabolism*
D005227:Fatty Acids; D006880:Hydroxy Acids; D008041:Linoleic Acids; D008054:Lipid Peroxides; C008285:linoleic acid hydroperoxide