Bernström K, Larsen G L, Hammarström S
Department of Medicine, Karolinska Institute, Huddinge Hospital, Sweden.
Arch Biochem Biophys. 1989 Dec;275(2):531-9. doi: 10.1016/0003-9861(89)90399-8.
Leukotriene E4 was incubated with cysteine-conjugate beta-lyase isolated from the intestinal bacterium Eubacterium limosum. The reaction was terminated by addition of iodoacetic acid or dimethyl sulfate, and the products formed were isolated by reverse-phase high-performance liquid chromatography. The structures of two adducts of a metabolite were determined by uv spectroscopy, by gas-liquid radiochromatography, and by comparisons with chemically synthesized reference compounds. They were 5-hydroxy-6-S-carboxymethylthio-7,9-trans-11,14-cis-eicosatetraeno ic acid (iodoacetic acid adduct) and 5-hydroxy-6-S-methylthio-7,9-trans-11,14-cis-eicosatetraenoic acid (dimethyl sulfate adduct) indicating that the structure of the underivatized metabolite was 5-hydroxy-6-mercapto-7,9,11,14-eicosatetraenoic acid (5,6-HMETE). The latter product is formed by beta-lyase-catalyzed cleavage of the cysteine C-S bond in leukotriene E4. Leukotriene E4 was also metabolized to 5,6-HMETE by rat cecal contents. A product formed was trapped as the iodoacetic acid derivative and identified as 5-hydroxy-6-S-carboxy-methylthio-7,9,11,14-eicosatetraenoic acid. It is concluded that intestinal leukotriene E4, originating from biliary excretion of systemic cysteinyl leukotrienes or produced in the intestine, is converted by microfloral cysteine-conjugate beta-lyase to 5,6-HMETE.
白三烯E4与从迟缓真杆菌这种肠道细菌中分离出的半胱氨酸共轭β-裂解酶一起孵育。通过添加碘乙酸或硫酸二甲酯终止反应，然后通过反相高效液相色谱法分离形成的产物。通过紫外光谱法、气液放射性色谱法以及与化学合成参考化合物进行比较，确定了一种代谢物的两种加合物的结构。它们分别是5-羟基-6-S-羧甲基硫基-7,9-反式-11,14-顺式-二十碳四烯酸（碘乙酸加合物）和5-羟基-6-S-甲硫基-7,9-反式-11,14-顺式-二十碳四烯酸（硫酸二甲酯加合物），这表明未衍生化代谢物的结构是5-羟基-6-巯基-7,9,11,14-二十碳四烯酸（5,6-HMETE）。后一种产物是由β-裂解酶催化白三烯E4中的半胱氨酸C-S键断裂形成的。白三烯E4也会被大鼠盲肠内容物代谢为5,6-HMETE。形成的一种产物被捕获为碘乙酸衍生物，并被鉴定为5-羟基-6-S-羧甲基硫基-7,9,11,14-二十碳四烯酸。得出的结论是，源自全身半胱氨酰白三烯胆汁排泄或在肠道中产生的肠道白三烯E4，会被微生物半胱氨酸共轭β-裂解酶转化为5,6-HMETE。
