Mechanism for the formation of dihydro metabolites of 12-hydroxyeicosanoids. Conversion of leukotriene B4 and 12-hydroxy-5,8,10,14-eicosatetraenoic acid to 12-oxo intermediates.

摘要: Eicosanoids containing a 12-hydroxyl group preceded by at least two conjugated double bonds are metabolized to 10,11-dihydro and 10,11-dihydro-12-oxo products porcine polymorphonuclear leukocytes (PMNL) (Wainwright, S. L., Falck, J. R., Yadagiri, P., Powell, W. (1990) Biochemistry 29, 10126-10135). These metabolites could either have been formed the direct reduction of 10,11-double bond substrate, as previous evidence suggested, or via an initially 12-oxo intermediate. To gain some insight into mechanism for formation dihydro this pathway, we investigated metabolism leukotriene B4 (LTB4), 12(S)-hydroxy-5,8,10,14-eicosatetraenoicacid(12(S)-HETE), 12(R)-HETE subcellular fractions from PMNL. In presence NAD+ microsomal fraction PMNL, each above 12-hydroxyeicosanoids was converted single product with lambda max approximately 40 nm higher than that indicating diene triene chromophore had extended one bond, presumably oxidation oxo group. case LTB4, confirmed mass spectrometry, which indicated identical 12-oxo-LTB4. LTB4 not any cytosolic but both 10,11-dihydro-LTB4 10,11-dihydro-12-oxo-LTB4 1500 x g supernatant in NAD+. Negligible amounts were NADH NADPH, suggesting initial is requirement bond. Consistent hypothesis, 12-oxo-LTB4 rapidly NADH. Only small product, along fraction. results indicate step 12-hydroxyeicosanoid dehydrogenase NAD+, followed olefinic delta 10-reductase