title: Hemoglobin degradation in the malaria parasite Plasmodium falciparum: an ordered process in a unique organelle.
abstract: The malaria parasite Plasmodium falciparum uses host erythrocyte hemoglobin as a major nutrient source. We report the purification of P. falciparum digestive vacuoles and characterization of the degradative process therein. Vacuoles were isolated by a combination of differential centrifugation and density gradient separation. The pure vacuoles were capable of degrading hemoglobin to small fragments with a pH optimum of 5-5.5. Proteolysis in the vacuoles appears to be an ordered process, requiring an aspartic protease to clip intact hemoglobin before other proteolytic activities can function efficiently. The vacuoles do not contain other hydrolases commonly found in lysosomes and therefore appear to be unique proteolytic organelles designed specifically to degrade hemoglobin.
authors.affiliation: Laboratory of Medical Biochemistry, Rockefeller University, New York, NY 10021.
authors.forename: D E
authors.initials: DE
authors.lastname: Goldberg
authors.forename: A F
authors.initials: AF
authors.lastname: Slater
authors.forename: A
authors.initials: A
authors.lastname: Cerami
authors.forename: G B
authors.initials: GB
authors.lastname: Henderson
mesh_terms: D000818:Animals; D002458:Cell Fractionation / Q000379:methods; D002499:Centrifugation, Density Gradient; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004912:Erythrocytes / Q000201:enzymology / Q000469:parasitology; D015801:Helminth Proteins; D006454:Hemoglobins / Q000378:metabolism*; D007700:Kinetics; D015388:Organelles / Q000201:enzymology*; D010963:Plasmodium falciparum / Q000201:enzymology*; D011480:Protease Inhibitors / Q000494:pharmacology; D011865:Radioisotope Dilution Technique; D051381:Rats; D011919:Rats, Inbred Strains; D012156:Reticulocytes / Q000201:enzymology / Q000469:parasitology; D014316:Tritium; D014617:Vacuoles / Q000201:enzymology* / Q000648:ultrastructure
chemical_list: D015801:Helminth Proteins; D006454:Hemoglobins; D011480:Protease Inhibitors; D014316:Tritium; D003546:Cysteine Endopeptidases