Purification and characterization of leukotriene A4 hydrolase from Xenopus laevis oocytes

In mammals, leukotriene A4 hydrolase converts leukotriene A4 into the proinflammatory mediator leukotriene B4. We have purified and characterized a non-mammalian leukotriene A4 hydrolase from Xenopus laevis oocytes. This enzyme contains one zinc atom and catalyzes an anion-dependent peptidase activity, two key features of the mammalian enzymes. The amino acid sequence of an internal segment is 60% identical with human leukotriene A4 hydrolase but only 27% identical with rat aminopeptidase B. The Xenopus laevis enzyme is catalytically very efficient and, unlike the human enzyme, converts leukotriene A4 into two enzymatic metabolites, viz. leukotriene B4 and delta6-trans-delta8-cis-leukotriene B4.