Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California-San Diego , 9500 Gilman Drive, La Jolla, California 92093-0934, United States.
Department of Chemistry, University of Texas at Austin , 105 East 24th Street, A5300, Austin, Texas 78712-1224, United States.
J Am Chem Soc. 2017 Apr 5;139(13):4943-4947. doi: 10.1021/jacs.7b01269. Epub 2017 Mar 28.
Lipids have fundamental roles in the structure, energetics, and signaling of cells and organisms. The recent discovery of fatty acid esters of hydroxy fatty acids (FAHFAs), lipids with potent antidiabetic and anti-inflammatory activities, indicates that our understanding of the composition of lipidome and the function of lipids is incomplete. The ability to synthesize and test FAHFAs was critical in elucidating the roles of these lipids, but these studies were performed with racemic mixtures, and the role of stereochemistry remains unexplored. Here, we synthesized the R- and S- palmitic acid ester of 9-hydroxystearic acid (R-9-PAHSA, S-9-PAHSA). Access to highly enantioenriched PAHSAs enabled the development of a liquid chromatography-mass spectrometry (LC-MS) method to separate and quantify R- and S-9-PAHSA, and this approach identified R-9-PAHSA as the predominant stereoisomer that accumulates in adipose tissues from transgenic mice where FAHFAs were first discovered. Furthermore, biochemical analysis of 9-PAHSA biosynthesis and degradation indicate that the enzymes and pathways for PAHSA production are stereospecific, with cell lines favoring the production of R-9-PAHSA and carboxyl ester lipase (CEL), a PAHSA degradative enzyme, selectively hydrolyzing S-9-PAHSA. These studies highlight the role of stereochemistry in the production and degradation of PAHSAs and define the endogenous stereochemistry of 9-PAHSA in adipose tissue. This information will be useful in the identification and characterization of the pathway responsible for PAHSA biosynthesis, and access to enantiopure PAHSAs will elucidate the role of stereochemistry in PAHSA activity and metabolism in vivo.
脂质在细胞和生物体的结构、能量学和信号转导中具有基本作用。最近发现的脂肪酸羟基脂肪酸酯（FAHFAs）是具有强大抗糖尿病和抗炎活性的脂质，这表明我们对脂质组的组成和脂质功能的理解并不完整。能够合成和测试 FAHFAs 对于阐明这些脂质的作用至关重要，但这些研究是用外消旋混合物进行的，立体化学的作用仍未得到探索。在这里，我们合成了 9-羟基硬脂酸的 R-和 S-棕榈酸酯（R-9-PAHSA，S-9-PAHSA）。获得高度对映体富集的 PAHSAs 使我们能够开发一种液相色谱-质谱（LC-MS）方法来分离和定量 R-和 S-9-PAHSA，这种方法确定 R-9-PAHSA 是在首次发现 FAHFAs 的转基因小鼠的脂肪组织中积累的主要立体异构体。此外，对 9-PAHSA 生物合成和降解的生化分析表明，PAHSA 产生的酶和途径具有立体特异性，细胞系有利于 R-9-PAHSA 的产生，而羧基酯脂肪酶（CEL）是一种 PAHSA 降解酶，选择性地水解 S-9-PAHSA。这些研究强调了立体化学在 PAHSA 产生和降解中的作用，并确定了脂肪组织中 9-PAHSA 的内源性立体化学。这些信息将有助于鉴定和表征负责 PAHSA 生物合成的途径，并且对映体纯的 PAHSAs 将阐明立体化学在体内 PAHSA 活性和代谢中的作用。
