title: Metabolism of leukotrienes.
abstract: The in vitro metabolism of leukotriene B4 is initiated by omega-hydroxylation. This reaction is followed by oxidation of the omega-hydroxyl group to a carboxyl group. In vivo extensive beta-oxidation occurs and the main excreted products after administration of leukotriene B4 are water and carbon dioxide. Experiments performed in vitro and in vivo have demonstrated that a major pathway of metabolism of the glutathione containing leukotrienes involves modifications of the tripeptide substituent. The metabolic alterations are initiated by enzymatic elimination of the N-terminal gamma-glutamyl residue, catalyzed by the enzyme gamma-glutamyl transferase. This reaction is followed by hydrolysis of the remaining peptide bond resulting in elimination of the C-terminal glycine residue. The enzyme catalyzing the latter reaction is a membrane bound dipeptidase which occurs in kidney and other tissues. The product formed by these reactions, leukotriene E4, has been tentatively identified as a urinary metabolite in man following intravenous administration of leukotriene C4. In rats, the two major fecal metabolities of leukotriene C4 were characterized as being N-acetyl leukotriene E4 and N-acetyl 11-trans leukotriene E4. These compounds are formed in reactions between leukotriene E4 or 11-trans leukotriene E4 and acetyl coenzyme A. The reactions are catalyzed by a membrane bound enzyme present in liver, kidney and other tissues.
mesh_terms: D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism*; D001711:Biotransformation; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D017572:Leukotriene A4; D007975:Leukotriene B4 / Q000378:metabolism*; D017999:Leukotriene E4; D008099:Liver / Q000378:metabolism; D010477:Perfusion; D013189:SRS-A / Q000031:analogs & derivatives / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D001095:Arachidonic Acids; D017572:Leukotriene A4; D013189:SRS-A; D007975:Leukotriene B4; D017999:Leukotriene E4