title: Comparison of proteases from chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum.
abstract: An aminopeptidase and four hemoglobin-degrading acid proteases have been isolated from cloned strains of chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum. Amino-peptidases from both strains showed similar properties including molecular weights of 63,000 and non-competitive inhibition by chloroquine; Ki = 535 and 410 microM for enzymes from the sensitive and resistant strains respectively. The acid proteases from the chloroquine-sensitive strain included a low molecular weight enzyme in the soluble fraction (protease S), an enzyme weakly associated with membrane (protease M2), and two enzymes strongly associated with membrane (proteases M3 and M4). The acid proteases from the chloroquine-resistant strain included protease S, protease M2, a second enzyme weakly associated with membrane (protease M1), and protease M3. All of the acid proteases were inhibited by ferriprotoporphyrin IX and by the chloroquine-ferriprotoporphyrin IX complex, I50 = 5-25 microM. The data were consistent with a model for chloroquine action wherein chloroquine acts to divert ferriprotoporphyrin IX from sequestration into malarial pigment, leaving ferriprotoporphyrin IX (or its chloroquine complex) to interfere with digestion of host cytosol by inhibiting hemoglobin-degrading proteases. However, the similarities among the proteases from chloroquine-sensitive and chloroquine-resistant strains of parasites suggest that chloroquine resistance does not result from changes in parasite proteases.
authors.affiliation: Department of Biochemistry, University of New Mexico, School of Medicine, Albuquerque 87131.
authors.forename: D L
authors.initials: DL
authors.lastname: Vander Jagt
authors.forename: L A
authors.initials: LA
authors.lastname: Hunsaker
authors.forename: N M
authors.initials: NM
authors.lastname: Campos
mesh_terms: D000626:Aminopeptidases / Q000032:analysis; D000818:Animals; D016282:Aspartic Acid Endopeptidases; D002738:Chloroquine / Q000494:pharmacology*; D004351:Drug Resistance; D010450:Endopeptidases / Q000032:analysis; D006427:Hemin / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D010436:Pepstatins / Q000494:pharmacology; D010447:Peptide Hydrolases / Q000032:analysis*; D010963:Plasmodium falciparum / Q000187:drug effects / Q000201:enzymology*; D011480:Protease Inhibitors
chemical_list: D010436:Pepstatins; D011480:Protease Inhibitors; C014195:Streptomyces pepsin inhibitor; D006427:Hemin; D002738:Chloroquine; D010450:Endopeptidases; D010447:Peptide Hydrolases; D000626:Aminopeptidases; D016282:Aspartic Acid Endopeptidases; C031375:pepstatin