title: Inhibition of a Plasmodium vinckei cysteine proteinase cures murine malaria.
abstract: Intraerythrocytic malaria parasites degrade hemoglobin as a principal source of amino acids for parasite protein synthesis. We have previously identified a Plasmodium falciparum trophozoite cysteine proteinase as a putative hemoglobinase and shown that specific inhibitors of this proteinase block the hydrolysis of globin and the development of cultured parasites. We now show that the murine malaria parasite Plasmodium vinckei has an analogous cysteine proteinase with similar biochemical properties to the P. falciparum proteinase, including an acid pH optimum, a preference for the peptide proteolytic substrate benzyloxycarbonyl (Z)-Phe-Arg-7-amino-4-methylcoumarin, and nonomolar inhibition by seven peptide fluoromethyl ketone proteinase inhibitors. Thus, P. vinckei offers a model system for the in vivo testing of the antimalarial properties of cysteine proteinase inhibitors. One of the proteinase inhibitors studied, morpholine urea (Mu)-Phe-Homophenylalanine (HPhe)-CH2F strongly inhibited the P. vinckei cysteine proteinase in vitro and rapidly blocked parasite cysteine proteinase activity in vivo. When administered four times a day for 4 d to P. vinckei-infected mice, Mu-Phe-HPhe-CH2F elicited long-term cures in 80% of the treated animals. These results show that peptide proteinase inhibitors can be effective antimalarial compounds in vivo and suggest that the P. falciparum cysteine proteinase is a promising target for chemotherapy.
authors.affiliation: Department of Medicine, San Francisco General Hospital, California.
authors.forename: P J
authors.initials: PJ
authors.lastname: Rosenthal
authors.forename: G K
authors.initials: GK
authors.lastname: Lee
authors.forename: R E
authors.initials: RE
authors.lastname: Smith
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology / Q000627:therapeutic use*; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D004151:Dipeptides / Q000494:pharmacology / Q000627:therapeutic use*; D007700:Kinetics; D008288:Malaria / Q000188:drug therapy*; D016778:Malaria, Falciparum / Q000188:drug therapy; D051379:Mice; D009025:Morpholines; D010961:Plasmodium / Q000187:drug effects / Q000201:enzymology* / Q000472:pathogenicity; D010963:Plasmodium falciparum / Q000187:drug effects / Q000472:pathogenicity; D013329:Structure-Activity Relationship
chemical_list: D000962:Antimalarials; D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D009025:Morpholines; C080182:P 34081; D003546:Cysteine Endopeptidases