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Title: Inhibition of a protein tyrosine kinase activity in Plasmodium falciparum by chloroquine
Authors: Sharma, Arun
Mishra, Neerad C
Issue Date: Oct-1999
Publisher: NISCAIR-CSIR, India
Abstract: The aim of the present study was to establish the importance of  phosphorylation events for parasite growth and maturation . Investigations into the cytosolic Plasmodium falciparum protein tyrosine kinase (PTK) activity revealed that there is a stage specific increase in the activity, in the order ring < trophozoite < schizont in both chloroquine sensitive (CQ-S) and chloroquine resistant (CQ-R) st rai ns (p<0.05). Our data also show that in vivo conversion of the schizont stage to ring stage via release of merozoites is associated with a decrease in PTK activity. Piceatannol, a specific inhibitor of PTK inhibited the activity in both the CQ-S and CQ-R strains of the parasites. The presence of low levels of chloroquine (CQ) inhibited the cytosolic PTK activity in a dose dependent manner (IC50 = 45 μmoles or 23 μg/ml ) in CQ-S strains. The effect of varying concentration of CQ on the kinetics of peptide phosphorylation reveal that CQ was a competitive inhibitor of PTK with respect to peptide substrate and non-competitive with respect to ATP indicating that CQ inhibits PTK activity by binding with protein substrate binding site. These data thus suggests that maturation of malaria parasite may be due to this cellular PTK and its inhibition by CQ could provide a hypothesis to explain its antimalarial activity and efficacy.
Page(s): 299-304
ISSN: 0975-0959 (Online); 0301-1208 (Print)
Appears in Collections:IJBB Vol.36(5) [October 1999]

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