Schistosoma mansoni: purification and characterization of a membrane-associated leucine aminopeptidase

Membrane-associated leucine aminopeptidase (EC 3.4.11.1, LAP) has been purified to homogeneity from Schistosoma mansoni egg homogenates by a combination of ultracentrifugation, chromatofocusing, and molecular sieve chromatography. A 260-fold increase in specific activity was observed after purification. This is a metalloenzyme, containing carbohydrate moieties. Optimal enzyme activity was found at neutral pH. Enzyme activity was measured using L-leucine-7-amino-4-trifluoromethylcoumarin (L-Leu-AFC); in addition, schistosome egg LAP hydrolyzed a variety of other aminopeptidase substrates. Hydrolysis of L-Leu-AFC was inhibited by a number of aminopeptidase inhibitors, including 1,10-phenanthroline, bestatin, and amastatin.