Browsing by Author "Scheepers, Melisse Sharne"

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    Investigation of Coenzyme A levels in Plasmodium falciparum to ascertain the mode of action of new antimalarial candidates
    (Stellenbosch : Stellenbosch University, 2017-03) Scheepers, Melisse Sharne; De Villiers, Marianne; Strauss, Erick; Stellenbosch University. Faculty of Science. Dept. of Biochemistry.
    ENGLISH ABSTRACT: The malaria parasite, Plasmodium falciparum, has become increasingly resistant to all commercially available drugs used in the treatment of malaria, and as such, the development of new antimalarial drugs with novel targets is of great importance. The coenzyme A (CoA) biosynthesis pathway is one such novel target since CoA and its precursor, pantothenate, have been shown to be essential for organism survival. N-phenethyl-α-methyl pantothenamide, a pantothenate analogue, has been shown in a previous study to inhibit growth in both bacteria and Plasmodium parasites, however the mode of action of this pantothenamide in Plasmodium is still unknown, and was thus investigated in this study. First, Plasmodiums’ requirement for pantothenate was investigated. We determined that parasites could survive without an extracellular source of pantothenate for up to eight days, however this contradicted what was found in literature, and was likely to be due to a Mycoplasma infection found late in the study. Secondly, it was investigated whether N-phenethyl-α-methyl pantothenamide can be metabolized to its CoA antimetabolites by the CoA biosynthetic enzymes present in P. falciparum. This was done by investigating the metabolism of the compound in both cell lysates and in in vivo P. falciparum cell cultures and it was found that PfPanK and PfDPCK is active in parasite lysates, while PfPPAT is inactive in parasite lysates. We could therefore not determine if the pantothenamide under investigation is being metabolized in the parasite by using lysates, but this is the first demonstration of the activity of PfDPCK in parasites lysate. Finally, we wanted to investigate the effect of tricyclic methylthiophenyl propanamide (TMP), a non-pantothenate analogue that inhibits the CoA biosynthesis pathway in other organisms, on P. falciparum proliferation. TMP was synthesized to use as a tool to investigate the mechanism of action of N-phenethyl-α-methyl pantothenamide to support that pantothenamides do not inhibit pantothenate kinase, as is known for TMP, but are rather metabolized downstream in the pathway. TMP was successfully synthesized and purified, however yields were too low to test TMP as an inhibitor of P. falciparum proliferation. Not only did the work done in this study shed more light on the mode of action of pantothenamides in P. falciparum, but also gave valuable insight into parasite biochemistry.