Kinetics of inhibition of glutathione-mediated degradation of ferriprotoporphyrin IX by antimalarial drugs

Famin, Oleg; Krugliak, Miriam; Ginsburg, Hagaï

doi:10.1016/s0006-2952(99)00059-3

Cited by 109 publications

(78 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Heme is released in large amounts by the parasite as a byproduct of hemoglobin degradation. Although heme accumulates in the parasite's food vacuole, where it crystallizes to hemozoin (32), a significant portion diffuses into the cytoplasm, where it is subject to glutathione-dependent degradation (33). In addition, heme is a prosthetic group for several parasite enzymes.…”

Section: Discussionmentioning

confidence: 99%

Illumination of the Malaria Parasite Plasmodium falciparum Alters Intracellular pH

Wissing

Sánchez

Rohrbach

et al. 2002

Journal of Biological Chemistry

View full text Add to dashboard Cite

Live cell fluorescence microscopy has been widely used to study physiological processes in the human malarial parasite Plasmodium falciparum, including pH homeostasis, Ca 2؉ signaling and protein targeting. However, the reproducibility of the data is often poor. Controversial statements exist regarding cytosolic and vacuolar baseline pH, as well as regarding the subcellular localization of some of the fluorochromes used. When trying to reproduce published baseline values, we observed an unexpected light sensitivity of P. falciparum, which manifests itself in the form of a strong cytoplasmic acidification. Even short exposure times with moderate to low light intensities caused the parasite cytosol to acidify. We show that this effect arises from the selective disruption of the parasite's acidic food vacuole, brought about by lipid peroxidation initiated by lightinduced generation of hydroxyl radicals. Our data suggest that heme serves as a photosensitizer in this process. Our findings have major implications for the use of live cell microscopy in P. falciparum and add a cautionary note to previous studies where live cell fluorometry has been used to determine physiological parameters in P. falciparum.Progress in understanding the physiology of the human malarial parasite Plasmodium falciparum has been slow, despite the fact that P. falciparum is a major health problem, killing millions of humans every year (1). As a consequence, only a limited number of potential drug targets have been identified in recent years. One reason for this is the obligatory intracellular life style of the parasite, which has complicated access to biochemical and physiological pathways.A powerful method to investigate physiological processes of intact cells, under non-disruptive conditions, is live cell fluorescence microscopy. This technique has recently been applied to the intraerythrocytic stages of P. falciparum for measuring intracellular pH, ion concentrations, Ca 2ϩ signaling, and protein targeting (2-7). The main advantage of live cell fluorescence microscopy is that it allows for the spatial separation of signals originating from the parasite and from the surrounding infected erythrocyte. Even subcellular compartments, such as the parasite's acidic food vacuole, can be visualized in situ using this method (5). However, a number of concerns have recently been raised about using single cell fluorescence microscopy in P. falciparum (8).A major disadvantage is the variability between cells, requiring a relatively large number of determinations to obtain statistically significant measurements. Reproducibility between different laboratories seems to be low as well when data obtained from single cell measurements are compared. For example, although some studies have found differences in the parasite's cytosolic pH between chloroquine-sensitive and chloroquine-resistant P. falciparum strains, other studies could not verify this observation (7, 9 -12). Another example represents the use of acridine orange (AO) 1 in the measurement of the...

show abstract

Section: Discussionmentioning

confidence: 99%

Illumination of the Malaria Parasite Plasmodium falciparum Alters Intracellular pH

Wissing

Sánchez

Rohrbach

et al. 2002

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…In fact, it has been shown that the parasitotoxic hemin inhibits PfGST uncompetitively (K i ϭ 6.5 M) indicating that free hemin can be bound by the enzyme in the micromolar range (13). Furthermore, it is known that chloroquine, one of the most important antimalarial drugs, inhibits hemin catabolism, leading to intracellular hemin accumulation (16). In chloroquine-resistant parasites, PfGST activity significantly increases compared with sensitive strains (17,18).…”

mentioning

confidence: 99%

Cooperativity and Pseudo-cooperativity in the Glutathione S-Transferase from Plasmodium falciparum

Liebau

Maria²,

Burmeister

et al. 2005

Journal of Biological Chemistry

View full text Add to dashboard Cite

Binding and catalytic properties of glutathione S-transferase from Plasmodium falciparum (PfGST) have been studied by means of fluorescence, steady state and pre-steady state kinetic experiments, and docking simulations. This enzyme displays a peculiar reversible low-high affinity transition, never observed in other GSTs, which involves the G-site and shifts the apparent K D for glutathione (GSH) from 200 to 0.18 mM. The transition toward the high affinity conformation is triggered by the simultaneous binding of two GSH molecules to the dimeric enzyme, and it is manifested as an uncorrected homotropic behavior, termed "pseudo-cooperativity." The high affinity enzyme is able to activate GSH, lowering its pK a value from 9.0 to 7.0, a behavior similar to that found in all known GSTs. Using 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, this enzyme reveals a potential optimized mechanism for the GSH conjugation but a low catalytic efficiency mainly due to a very low affinity for this co-substrate. Conversely, PfGST efficiently binds one molecule of hemin/monomer. The binding is highly cooperative (n H ‫؍‬ 1.8) and occurs only when GSH is bound to the enzyme. The thiolate of GSH plays a crucial role in the intersubunit communication because no cooperativity is observed when S-methylglutathione replaces GSH. Docking simulations suggest that hemin binds to a pocket leaning into both the G-site and the H-site. The iron is coordinated by the amidic nitrogen of Asn-115, and the two carboxylate groups are in electrostatic interaction with the ⑀-amino group of Lys-15. Kinetic and structural data suggest that PfGST evolved by optimizing its binding property with the parasitotoxic hemin rather than its catalytic efficiency toward toxic electrophilic compounds.

show abstract

“…Malaria-infected erythrocytes are characterized by a high rate of production of ferriprotoporphyrin IX (heme) as a result of the ingestion and digestion of host cell haemoglobin (Famin et al, 1999). The parasite utilizes hemoglobin as its primary food source during intraerythrocytic development and proliferation (Francis et al, 1997).…”

Section: Resultsmentioning

confidence: 99%

Evaluation of antimalarial, free-radical-scavenging and insecticidal activities of Artemisia scoparia and A. Spicigera, Asteraceae

Afshar¹,

Delazar²,

Janneh³

et al. 2011

Rev. bras. farmacogn.

View full text Add to dashboard Cite

Artemisia species (Asteraceae), widespread throughout the world, are a group of important medicinal plants. The extracts of two medicinal plants of this genus, Artemisia scoparia Waldst. & Kit. and A. spicigera C. Koch, were evaluated for potential antimalarial, free-radical-scavenging and insecticidal properties, using the heme biocrystallisation and inhibition assay, the DPPH assay and the contact toxicity bioassay using the pest Tribolium castaneum, respectively. The methanol extracts of both species showed strong free-radical-scavenging activity and the RC50 values were 0.0317 and 0.0458 mg/mL, respectively, for A. scoparia and A. spicigera. The dichloromethane extracts of both species displayed a moderate level of potential antimalarial activity providing IC50 at 0.778 and 0.999 mg/mL for A. scoparia and A. spicigera, respectively. Both species of Artemisia showed insecticidal properties. However, A. spicigera was more effective than A. scoparia.

show abstract

Kinetics of inhibition of glutathione-mediated degradation of ferriprotoporphyrin IX by antimalarial drugs

Cited by 109 publications

References 58 publications

Illumination of the Malaria Parasite Plasmodium falciparum Alters Intracellular pH

Illumination of the Malaria Parasite Plasmodium falciparum Alters Intracellular pH

Cooperativity and Pseudo-cooperativity in the Glutathione S-Transferase from Plasmodium falciparum

Evaluation of antimalarial, free-radical-scavenging and insecticidal activities of Artemisia scoparia and A. Spicigera, Asteraceae

Contact Info

Product

Resources

About