title: Enzymatic hydration of leukotriene A4. Purification and characterization of a novel epoxide hydrolase from human erythrocytes.
abstract: Human erythrocytes contained a soluble cytosolic epoxide hydrolase for stereospecific enzymatic hydration of leukotriene A4 into leukotriene B4. The enzyme was purified 1100-fold, to apparent electrophoretic homogeneity, by conventional DEAE-Sephacel fractionation followed by high performance anion exchange and chromatofocusing procedures. Its characteristics include a molecular weight of 54,000 +/- 1,000, an isoelectric point 4.9 +/- 0.2, a Km apparent from 7 to 36 microM for enzymatic hydration of leukotriene A4, and a pH optimum ranging from 7 to 8. The enzyme was partially inactivated by its initial exposure to leukotriene A4. There was slow but detectable enzymatic hydration (pmol/min/mg) of certain arachidonic acid epoxides including (+/-)-14,15-oxido-5,8-11-eicosatrienoic acid and (+/-)-11,12-oxido-5,8,14-eicosatrienoic acid, but not others, including 5,6-oxido-8,11,14-eicosatrienoic acid. Human erythrocyte epoxide hydrolase did not hydrate either styrene oxide or trans-stilbene oxide. In terms of its physical properties and substrate preference for leukotriene A4, the erythrocyte enzyme differs from previously described versions of epoxide hydrolase. Human erythrocytes represent a novel source for an extrahepatic, cytosolic epoxide hydrolase with a potential physiological role.
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001095:Arachidonic Acids / Q000378:metabolism* / Q000494:pharmacology; D002845:Chromatography; D003600:Cytosol / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D004851:Epoxide Hydrolases / Q000037:antagonists & inhibitors / Q000097:blood* / Q000302:isolation & purification; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D007526:Isoelectric Point; D017572:Leukotriene A4; D007975:Leukotriene B4 / Q000378:metabolism; D008970:Molecular Weight; D013267:Stilbenes / Q000494:pharmacology; D013379:Substrate Specificity
chemical_list: D001095:Arachidonic Acids; D017572:Leukotriene A4; D013267:Stilbenes; D007975:Leukotriene B4; C046783:11,12-epoxy-5,8,14-eicosatrienoic acid; C046782:14,15-epoxy-5,8,11-eicosatrienoic acid; D004851:Epoxide Hydrolases; D015126:8,11,14-Eicosatrienoic Acid; C025906:stilbene oxide