NAD+-dependent oxidation of 20-hydroxyleukotriene B4 to 20-carboxyleukotriene B4 by rat liver cytosol.

20-Hydroxyleukotriene B4 was converted by rat liver homogenates in the presence of NAD+ to a more polar product on reverse-phase high-performance liquid chromatography. The product was identified as 20-carboxyleukotriene B4 by straight-phase high performance liquid chromatography, ultraviolet spectrophotometry and gas chromatography-mass spectrometry. The oxidative activity of the homogenates was located in the cytosol with an optimal pH of 8.0. The activity was dependent on NAD+, and NADP+ could not substitute for NAD+. 1 mol of 20-carboxyleukotriene B4 was formed with the reduction of 2 mol of NAD+. The reaction was inhibited by pyrazole and 4-methylpyrazole, inhibitors of alcohol dehydrogenase, and by various alcohols, such as ethanol, 12-hydroxylaurate, and 20-hydroxyprostaglandin E1. Disulfiram, an inhibitor of aldehyde dehydrogenase, also inhibited the activity. These results suggest that two discrete steps catalyzed by different enzymes, alcohol dehydrogenase and aldehyde dehydrogenase, are involved in the oxidation of 20-hydroxyleukotriene B4 in rat liver cytosol. The enzyme system seems to be different from that of human neutrophils.