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Novel oxylipins formed from docosahexaenoic acid by potato lipoxygenase—10( S )‐hydroxydocosahexaenoic acid and 10,20‐dihydroxydocosahexaenoic acid
Author(s) -
Butovich Igor A.,
Hamberg Mats,
Rådmark Olof
Publication year - 2005
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-005-1379-z
Subject(s) - docosahexaenoic acid , lipoxygenase , lipidology , clinical chemistry , chemistry , oxylipin , biochemistry , fatty acid , food science , polyunsaturated fatty acid , enzyme
Potato tuber lipoxygenase (ptLOX) has been shown to catalyze the aerobic formation of at least four major oxygenated derivatives of DHA. Two of the products—7,17( S )‐ and 10,17( S )‐dihydro(pero)xy‐DHA [7,17‐ and 10,17‐diH(P)DHA]— were formed from soybean 15‐LOX‐derived 17( S )‐hydro(pero)xy‐DHA [17( S )‐H(P)DHA], whereas two novel oxylipin compounds— 10( S )‐hydro(pero)xy‐DHA and 10,20‐dihydro(pero)xy‐DHA [10( S )‐H(P)DHA and 10,20‐diH(P)DHA, respectively]—were the major direct products of DHA oxidation by ptLOX. The reactions proceeded relatively slowly but could be stimulated by catalytic amounts of SDS. Micromolar concentrations of 10( S )‐HPDHA effectively abolished the kinetic lag period of ptLOX activation. Enzymatic activity with DHA or 17( S )‐HPDHA as substrate was about 8% of that with linoleic acid—a standard natural ptLOX substrate—whereas 17( S )‐HDHA was converted at a rate of ∼1%. The enzyme was relatively unstable and quickly inactivated during the reaction with DHA on with 17( S )‐HPDHA (first‐order kinetic constant of inactivation k in =1.5±0.3 min −1 ), but not with 17( S )‐HDHA. Both 7,17‐ and 10,20‐diH(P)DHA were clearly products of double oxygenation catalyzed by soybean 15‐LOX and/or ptLOX. Our observation that ptLOX could convert 17‐HDHA to 10,17‐diH(P)DHA indicates that this dihydroxylated derivative of DHA also can be formed via a double lipoxygenation mechanism.