Department Biochemistry & Microbiology, Rhodes University, Grahamstown, SOUTH AFRICA
Title: In vivo; in vitro interaction of silver nanoparticles with leucine aminopeptidase from human and Plasmodium falciparum.
Biography: Chris Whiteley
Statement of the Problem: There is increasing requirement for the development of new drug protocols against malaria, a fatal disease caused by the lethal parasite Plasmodium falciparum. Leucine aminopeptidase (PfLAP) of Plasmodium falciparum, is being pursued as a promising target for the discovery of novel antimalarials.. Methodology: PfLAP and HsLAP were expressed in Escherichia coli, and AgNPs (3-10 nm) characterized by ultra-violet spectroscopy and transmission electron microscopy. The effects of silver nanoparticles (AgNPs) against P. falciparum leucine amino-peptidase (PfLAP) and the human homolog (HsLAP) were compared. Findings: PfLAP indicated a Km of 694 µM towards leucine-p-nitroanilide and a Vmax of 57.9 μmol.ml-1.min-1 while HsLAP had a Km of 1.6 mM and Vmax of 119.6 μmol.ml-1.min-1. On interaction with AgNPs (670 nM) PfLAP was selectively inhibited (57.1 %; Ki = 610 nM) relative to HsLAP (10.8 %; Ki = 5.22 µM). The viability of P. falciparum parasites was decreased when exposed to silver nanoparticles, with an IC50 value of 6.96 μM, compared to an IC50 value of 647.7 μM for human HeLa cells. Conclusion & Significance: Structural differences between the enzyme variants, particularly the orientation and distance of surface Met349 in PfLAP and Met306 in HsLAP to the zinc binding sites were significant and may allow for selective targeting of PfLAP by AgNPs.