A proposed beneficial impact of highly unsaturated "fish oil" fatty acids is their conversion by lipoxygenase (LOX) enzymes to specialized proresolving lipid mediators, including 12/15-LOX products from EPA and DHA. The transformations of DHA include formation of docosatrienes, named for the distinctive conjugated triene of the double bonds. To further the understanding of biosynthetic pathways and mechanisms, herein we meld together biosynthesis and NMR characterization of the unstable leukotriene A (LTA)-related epoxide intermediates formed by recombinant human 15-LOX-1, along with identification of the stable enzymatic products, and extend the findings into the 12/15-LOX metabolism in resident murine peritoneal macrophages. Oxygenation of EPA by 15-LOX-1 converts the initial 15S-hydroperoxide to 14S,15S-trans-epoxy-5Z,8Z,10E,12E,17Z-EPA (appearing as its 8,15-diol hydrolysis products) and mixtures of dihydroperoxy fatty acids, while mainly the epoxide hydrolysis products are evident in the murine cells. DHA also undergoes transformations to epoxides and dihydroperoxides by 15-LOX-1, resulting in a mixture of 10,17-dihydro(pero)xy derivatives (docosatrienes) and minor 7S,17S- and 14,17S-dihydroperoxides. The 10,17S-dihydroxy hydrolysis products of the LTA-related epoxide intermediate dominate the product profile in mouse macrophages, whereas (neuro)protectin D1, the leukotriene B4-related derivative with trans,trans,cis conjugated triene, was undetectable. In this study, we emphasize the utility of UV spectral characteristics for product identification, being diagnostic of the different double bond configurations and hydroxy fatty acid functionality versus hydroperoxide. LC-MS is not definitive for configurational isomers. Secure identification is based on chromatographic retention times, comparison with authentic standards, and the highly distinctive UV spectra.

中文翻译：

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分析 EPA 和 DHA 的 12/15-脂氧合酶代谢，特别注意二十二碳三烯的鉴定。

高度不饱和“鱼油”脂肪酸的一个提议的有益影响是它们通过脂氧合酶 (LOX) 酶转化为专门的促分解脂质介质，包括来自 EPA 和 DHA 的 12/15-LOX 产品。DHA 的转化包括形成二十二碳三烯，以独特的双键共轭三烯命名。为了进一步了解生物合成途径和机制，我们将重组人 15-LOX-1 形成的不稳定白三烯 A (LTA) 相关环氧化物中间体的生物合成和 NMR 表征结合在一起，并鉴定了稳定的酶产物，以及将研究结果扩展到常驻小鼠腹腔巨噬细胞的 12/15-LOX 代谢。15-LOX-1 对 EPA 的氧化将最初的 15S-氢过氧化物转化为 14S,15S-trans-epoxy-5Z,8Z,10E,12E, 17Z-EPA（作为其 8,15-二醇水解产物出现）和二氢过氧脂肪酸的混合物，而在鼠细胞中主要是环氧化物水解产物。DHA 还通过 15-LOX-1 转化为环氧化物和二氢过氧化物，产生 10,17-二氢（过）xy 衍生物（二十二碳三烯）和少量 7S,17S-和 14,17S-二氢过氧化物的混合物。LTA 相关环氧化物中间体的 10,17S-二羟基水解产物在小鼠巨噬细胞中占主导地位，而 (神经) 保护素 D1，白三烯 B4 相关衍生物，具有反式、反式、顺式共轭三烯，无法检测到。在这项研究中，我们强调了紫外光谱特性在产品鉴定中的效用，即不同双键构型和羟基脂肪酸功能与氢过氧化物的诊断。LC-MS 不能确定构型异构体。安全鉴定基于色谱保留时间、与真实标准品的比较以及高度独特的紫外光谱。