Abstract
The identification of extra-functional activities of enzymes is an attractive strategy for development of new antiparasitic drugs. In this study, the nuclease properties of Plasmodium Nucleoside Diphosphate Kinase (PfNDK) were demonstrated. The classical effect of PfNDK is the production of nucleotides for DNA/RNA synthesis. Such new nuclease activity of PfNDK implies the incrimination of the enzyme in functions other than its classical kinase activity. Such functions include apoptosis, regulation of cell cycle, cell division and repair of DNA damage. We have investigated the nuclease activity of Plasmodium falciparum Nucleoside Diphosphate Kinase (PfNDK). The nature of the nucleotide sequence and the length of the DNA substrate were critical factors in PfNDK's nuclease activity. The PfNDK was unable to bind to oligonucleotides, although it formed aggregates with oligonucleotides that contained repeated pyrimidine nucleotides in their sequence. The enzyme was unable to cleave a supercoiled plasmid, whereas DNA substrates of various lengths were cleaved in a time- and concentration-dependent manner. Furthermore, ATP at a concentration of 1 mM was able to inhibit the nuclease activity. These data is valuable in highlighting the possible role of PfNDK in cellular functions other than its classical nucleotide kinase activity. Specific PfNDK inhibition is expected to modulate parasites cell cycle and induction of apoptosis.