Novel oxylipins formed from docosahexaenoic acid by potato lipoxygenase—10(S)‐hydroxydocosahexaenoic acid and 10,20‐dihydroxydocosahexaenoic acid

Abstract

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 approximately 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 kin = 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.

Anti-Inflammatory Actions of Neuroprotectin D1/Protectin D1 and Its Natural Stereoisomers: Assignments of Dihydroxy-Containing Docosatrienes

“…47; doctoral thesis with C. Reddy as advisor). Recently, classic steric analysis of 10S-HDHA and the formation of 10,20-diHDHA and 17-H(p)DHA were reportedly optimized for the plant LOs (49). In the present studies, the double dioxygenation product prepared, matched, and identified in both suspensions of human PMN ( Fig.…”

Lithium modifies brain arachidonic and docosahexaenoic metabolism in rat lipopolysaccharide model of neuroinflammation

“…The enzymatic conversion of DHA to docosanoids has not been fully characterized but appears to involve an initial conversion of DHA to 17 S -hydroxy-DHA (17-OH-DHA) by a 15 -lipoxygenase (LOX)-like enzyme and further conversion to resolvins D via epoxide intermediates ( 13 ). So far, only isolated soybean and potato 15-LOX and porcine 12-LOX have been shown to convert DHA to 17-OH-DHA in vitro ( 10,14,15 ). In addition, the oxygenation of DHA to 17-OH-DHA can be mediated by nonenzymatic autoxidation ( 16 ).…”

Human tear film and meibum. Very long chain wax esters and (O-acyl)-omega-hydroxy fatty acids of meibum

“…6, 9, 10 ) made it possible to characterize WE and related compounds to a much better degree than before. It be- chromatography (GLC) or GC-MS ( 28 ). The experiments are in progress to address these issues.…”