title: Degradation of human IgA by Entamoeba histolytica.
abstract: To determine whether the virulent enteric pathogen Entamoeba histolytica degrades human IgA molecules, serum and secretory IgA was exposed to viable axenic trophozoites (strain HM1:IMSS), a parasite sonicate, and medium conditioned by incubation with live trophozoites. IgA was completely degraded under all conditions, proteinase activity was maximal at a neutral pH, and there was a four- to eightfold enrichment of amebic IgA proteolytic activity in a soluble fraction of amebic sonicate. Degradation of serum IgA by amebic sonicate was completely inhibited by the cysteine proteinase inhibitors trans-epoxysuccinyl-L-leucyl-amino(4-guanidino)butane (E-64, 100 microM) and benzyloxycarbonyl-phenyl-alanyl-alanyl-fluoromethyl (Z-Phe-Ala-CH2F, 12.5 microM). Secretion of degradative activity, the optimal pH, and the inhibition by E-64 and Z-Phe-Ala-CH2F indicates that cysteine proteinase activity is predominantly responsible for the degradation of human IgA by E. histolytica.
authors.affiliation: Division of Infectious Diseases, University of Virginia Medical Center, Charlottesville.
authors.forename: B L
authors.initials: BL
authors.lastname: Kelsall
authors.forename: J I
authors.initials: JI
authors.lastname: Ravdin
mesh_terms: D000818:Animals; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D004748:Entamoeba histolytica / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D007070:Immunoglobulin A / Q000378:metabolism*; D007659:Ketones / Q000494:pharmacology; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D013347:Subcellular Fractions / Q000201:enzymology / Q000378:metabolism
chemical_list: D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D007070:Immunoglobulin A; D007659:Ketones; C057383:MDL 201053; D003546:Cysteine Endopeptidases; D007930:Leucine; C024974:E 64