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Title: Functional analysis, overexpression, and kinetic characterization of pyruvate kinase from Plasmodium falciparum
Authors: Chan, M.
Sim, T.-S. 
Keywords: cDNA cloning
Plasmodium falciparum
Pyruvate kinase
Issue Date: 2004
Citation: Chan, M., Sim, T.-S. (2004). Functional analysis, overexpression, and kinetic characterization of pyruvate kinase from Plasmodium falciparum. Biochemical and Biophysical Research Communications 326 (1) : 188-196. ScholarBank@NUS Repository.
Abstract: The important role of pyruvate kinase during malarial infection has prompted the cloning of a cDNA encoding Plasmodium falciparum pyruvate kinase (pfPyrK), using mRNA from intraerythrocytic-stage malaria parasites. The full-length cDNA encodes a protein with a computed molecular weight of 55.6 kDa and an isoelectric point of 7.5. The purified recombinant pfPyrK is enzymatically active and exists as a homotetramer in its active form. The enzyme exhibits hyperbolic kinetics with respect to phosphoenolpyruvate and ADP, with Km of 0.19 and 0.12 mM, respectively. pfPyrK is not affected by fructose-1,6-bisphosphate, a general activating factor of pyruvate kinase for most species. Glucose-6-phosphate, an activator of the Toxoplasma gondii enzyme, does not affect pfPyrK activity. Similar to rabbit pyruvate kinase, pfPyrK is susceptible to inactivation by 1 mM pyridoxal-5′-phosphate, but to a lesser extent. A screen for inhibitors to pfPyrK revealed that it is markedly inhibited by ATP and citrate. Detailed kinetic analysis revealed a transition from hyperbolic to sigmoidal kinetics for PEP in the presence of citrate, as well as competitive inhibitory behavior for ATP with respect to PEP. Citrate exhibits non-competitive inhibition with respect to ADP with a Ki of 0.8 mM. In conclusion, P. falciparum expresses an active pyruvate kinase during the intraerythrocytic-stage of its developmental cycle that may play important metabolic roles during infection. © 2004 Elsevier Inc. All rights reserved.
Source Title: Biochemical and Biophysical Research Communications
ISSN: 0006291X
DOI: 10.1016/j.bbrc.2004.11.018
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