title: Leucine aminopeptidase of the human blood flukes, Schistosoma mansoni and Schistosoma japonicum.
abstract: An array of schistosome endoproteases involved in the digestion of host hemoglobin to absorbable peptides has been described, but the exoprotease responsible for catabolising these peptides to amino acids has yet to be identified. By searching the public databases we found that Schistosoma mansoni and Schistosoma japonicum express a gene encoding a member of the M17 family of leucine aminopeptidases (LAPs). A functional recombinant S. mansoni LAP produced in insect cells shared biochemical properties, including pH optimum for activity, substrate specificity and reliance on metal cations for activity, with the major aminopeptidase activity in soluble extracts of adult worms. The pH range in which the enzyme functions and the lack of a signal peptide indicate that the enzyme functions intracellularly. Immunolocalisation studies showed that the S. mansoni LAP is synthesised in the gastrodermal cells surrounding the gut lumen. Accordingly, we propose that peptides generated in the lumen of the schistosome gut are absorbed into the gastrodermal cells and are cleaved by LAP to free amino acids before being distributed to the internal tissues of the parasite. Since LAP was also localised to the surface tegument it may play an additional role in surface membrane re-modelling.
authors.affiliation: Molecular Parasitology Unit, School of Biotechnology, Dublin City University, Dublin 9, Ireland.
authors.forename: Elaine
authors.initials: E
authors.lastname: McCarthy
authors.forename: Colin
authors.initials: C
authors.lastname: Stack
authors.forename: Sheila M
authors.initials: SM
authors.lastname: Donnelly
authors.forename: Sean
authors.initials: S
authors.lastname: Doyle
authors.forename: Victoria H
authors.initials: VH
authors.lastname: Mann
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Brindley
authors.forename: Michael
authors.initials: M
authors.lastname: Stewart
authors.forename: Tim A
authors.initials: TA
authors.lastname: Day
authors.forename: Aaron G
authors.initials: AG
authors.lastname: Maule
authors.forename: John P
authors.initials: JP
authors.lastname: Dalton
mesh_terms: D000042:Absorption; D000595:Amino Acid Sequence; D000818:Animals; D002412:Cations / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007931:Leucyl Aminopeptidase / Q000378:metabolism*; D018613:Microscopy, Confocal / Q000379:methods; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics; D012547:Schistosoma / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D012549:Schistosoma japonicum / Q000145:classification / Q000201:enzymology / Q000235:genetics; D012550:Schistosoma mansoni / Q000145:classification / Q000201:enzymology / Q000235:genetics; D013379:Substrate Specificity
chemical_list: D002412:Cations; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D007931:Leucyl Aminopeptidase