title: Metabolism of leukotriene E4 to 5-hydroxy-6-mercapto7,9-trans-11,14-cis-eicosatetraenoic acid by microfloral cysteine-conjugate beta-lyase and rat cecum contents.
abstract: 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.
authors.affiliation: Department of Medicine, Karolinska Institute, Huddinge Hospital, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Bernström
authors.forename: G L
authors.initials: GL
authors.lastname: Larsen
authors.forename: S
authors.initials: S
authors.lastname: Hammarström
mesh_terms: D000818:Animals; D013437:Carbon-Sulfur Lyases; D002432:Cecum / Q000382:microbiology*; D002851:Chromatography, High Pressure Liquid; D005051:Eubacterium / Q000201:enzymology* / Q000302:isolation & purification; D005766:Gastrointestinal Contents / Q000382:microbiology*; D017999:Leukotriene E4; D008190:Lyases / Q000378:metabolism*; D013058:Mass Spectrometry; D051381:Rats; D013189:SRS-A / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet
chemical_list: D013189:SRS-A; C062039:5-hydroxy-6-mercapto-7,9,11,14-eicosatetraenoic acid; D017999:Leukotriene E4; D008190:Lyases; D013437:Carbon-Sulfur Lyases; C019969:S-alkylcysteine lyase