Oxalate: A potential ligand for differentiating Plasmodium berghei lactate dehydrogenase from host erythrocyte lactate dehydrogenase

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University of Ilorin Library and Publication Committee


Plasmodium lactate dehydrogenase is a valuable malaria diagnostic indicator. However, the difference between Plasmodium and host lactate dehydrogenase (LDH) activities in the presence of ligands has not been fully characterized. This study investigated the effects of Co2+ and oxalate on lactate dehydrogenase activities in Plasmodium berghei-infected erythrocyte (PBIE-LDH) and uninfected erythrocytes (UE-LDH) of mice. LDH activities in PBIE and UE were determined in the presence of varying concentrations of Co2+ and oxalate. Vmax of PBIE-LDH was three times higher (with reduced Km) than that of UE-LDH in the absence of the ligands. Co2+ activated both PBIE-LDH and UE-LDH activities with optimal concentrations at 10 mM and 5 mM respectively. Oxalate (0.1-10 mM) inhibited UE-LDH activity. Moreover, oxalate (from 0.1 to 2 mM) progressively inhibited PBIE-LDH activity but concentrations higher than 2 mM (up to 10 mM) progressively reversed this inhibition but not to the range of the enzyme activity in the absence of oxalate. Kinetic analyses revealed that Vmax of PBIE-LDH in the presence of 5 mM oxalate and 5 mM Co2+ was one and a half times and five times higher (with reduced Km) than those of UE-LDH respectively. These results suggest that the P. berghei LDH can be differentiated from host erythrocyte LDH in the presence of oxalate at concentrations higher than 2 mM. This could be of significance in antimalarial screening programmes and, by extension, effective diagnosis of malaria caused by other Plasmodium species and monitoring of recovery during treatment.



Lactate dehydrogenase, Plasmodium, ligands, malaria diagnosis