Final Report Summary - VITBIOMAL (Vitamin biosynthesis as a target for antimalarial therapy)
Plasmodium falciparum causes severe malaria and about 2 million human deaths annually. The main obstacle to combat the disease is increasing resistance of the parasites to existing drugs and the lack of a protective vaccine. Therefore, it is imperative that new suitable drug targets in the parasite's metabolism are identified, assessed and validated. The availability of the parasite's genome sequence offers an excellent tool to identify metabolic pathways potentially essential for parasite survival. Scrutinising the Plasmodium genomes revealed that they possess biosynthetic pathways for vitamins.
The aim of 'Vitamin biosynthesis as a target for antimalarial therapy' (VITBIOMAL) was to specifically assess vitamin B6 de novo biosynthesis of Plasmodium as target for antimalarial drug development. To do so, the precise role of de novo biosynthesis versus uptake for the overall regulation of vitamin B6 homeostasis in the parasites will be established.
Vitamins are organic compounds required in small amounts to ensure normal metabolic functions. Since they are not synthesised by humans, they need to be supplied via nutrients in trace amounts. The absence of vitamin biosynthesis in humans suggests that specific targeting of these parasite pathways with inhibitors is feasible. Thus, vitamin biosynthesis of Plasmodium might offer excellent potential for the development of novel chemotherapeutics against malaria with specific toxicity towards the parasites without affecting the host's metabolism. In the first instance, the project will focus on vitamin B6 biosynthesis, as this important nutrient is required as a co-factor for a wide variety of essential metabolic functions in protein and amino acid metabolism, and has also has been implicated in the defence against oxidative stress in other eukaryotes. Using reverse genetic approaches, they aimed to validate the suitability of two of the vitamin B6 synthesising enzymes Pdx1 and Pdx2 respectively as drug targets. In addition, their precise biological functions and potential interactions with other cellular components will be analysed. Further, the biochemical, biophysical and structural features of both enzymes was to be assessed in order to be able to rationally design specific inhibitors that interfere with the parasite's proteins activities and functions.
Vitamin B6 is one of nature's most versatile cofactors. Most organisms synthesise vitamin B6 via a recently discovered pathway employing the proteins Pdx1 and Pdx2. In course of this project it turned out that Pdx1 is the actual synthase of the complex synthesising the biological active B6 vitamer pyridocal-5-phosphate (PLP) from NH3 which is provided by the glutamise partner Pdx2 and ordinary sugars.
The project has done an in depth characterisation of the respective orthologs from the malaria parasite, Plasmodium falciparum. Expression profiling of Pdx1 and 2 revealed that parasite blood stages possess a functional vitamin B6 de novo biosynthesis. Using reverse genetic approaches the suitability the vitamin B6 synthesising enzymes Pdx1 and Pdx2 as drug targets was investigated. Gene knock-out studies in the mouse malaria model system revealed that the parasite possesses a functional vitamin B6 uptake system, which can at least in part compensate for loss of function of de novo biosynthesis, suggesting that the latter is not essential for parasite survival and as a consequence not a suitable target for antimalarial drug development. The contribution of vitamin B6 uptake and/or salvage versus vitamin B6 de novo biosynthesis to the overall PLP homeostasis was addressed by vitamin B6 depletion experiments and by gene knock-outs affecting either parasite's de novo vitamin B6 biosynthesis or vitamin B6 uptake and/or salvage.
Although the projects studies has ruled out vitamin B6 de novo biosynthesis as a suitable target for antimalarial drug development, the project had a tremendous impact on the biological, biochemical biophysical and structural characterisation of the vitamin B6 synthesising enzyme complex and pushed on the knowledge and expertise on this topic significantly.
The aim of 'Vitamin biosynthesis as a target for antimalarial therapy' (VITBIOMAL) was to specifically assess vitamin B6 de novo biosynthesis of Plasmodium as target for antimalarial drug development. To do so, the precise role of de novo biosynthesis versus uptake for the overall regulation of vitamin B6 homeostasis in the parasites will be established.
Vitamins are organic compounds required in small amounts to ensure normal metabolic functions. Since they are not synthesised by humans, they need to be supplied via nutrients in trace amounts. The absence of vitamin biosynthesis in humans suggests that specific targeting of these parasite pathways with inhibitors is feasible. Thus, vitamin biosynthesis of Plasmodium might offer excellent potential for the development of novel chemotherapeutics against malaria with specific toxicity towards the parasites without affecting the host's metabolism. In the first instance, the project will focus on vitamin B6 biosynthesis, as this important nutrient is required as a co-factor for a wide variety of essential metabolic functions in protein and amino acid metabolism, and has also has been implicated in the defence against oxidative stress in other eukaryotes. Using reverse genetic approaches, they aimed to validate the suitability of two of the vitamin B6 synthesising enzymes Pdx1 and Pdx2 respectively as drug targets. In addition, their precise biological functions and potential interactions with other cellular components will be analysed. Further, the biochemical, biophysical and structural features of both enzymes was to be assessed in order to be able to rationally design specific inhibitors that interfere with the parasite's proteins activities and functions.
Vitamin B6 is one of nature's most versatile cofactors. Most organisms synthesise vitamin B6 via a recently discovered pathway employing the proteins Pdx1 and Pdx2. In course of this project it turned out that Pdx1 is the actual synthase of the complex synthesising the biological active B6 vitamer pyridocal-5-phosphate (PLP) from NH3 which is provided by the glutamise partner Pdx2 and ordinary sugars.
The project has done an in depth characterisation of the respective orthologs from the malaria parasite, Plasmodium falciparum. Expression profiling of Pdx1 and 2 revealed that parasite blood stages possess a functional vitamin B6 de novo biosynthesis. Using reverse genetic approaches the suitability the vitamin B6 synthesising enzymes Pdx1 and Pdx2 as drug targets was investigated. Gene knock-out studies in the mouse malaria model system revealed that the parasite possesses a functional vitamin B6 uptake system, which can at least in part compensate for loss of function of de novo biosynthesis, suggesting that the latter is not essential for parasite survival and as a consequence not a suitable target for antimalarial drug development. The contribution of vitamin B6 uptake and/or salvage versus vitamin B6 de novo biosynthesis to the overall PLP homeostasis was addressed by vitamin B6 depletion experiments and by gene knock-outs affecting either parasite's de novo vitamin B6 biosynthesis or vitamin B6 uptake and/or salvage.
Although the projects studies has ruled out vitamin B6 de novo biosynthesis as a suitable target for antimalarial drug development, the project had a tremendous impact on the biological, biochemical biophysical and structural characterisation of the vitamin B6 synthesising enzyme complex and pushed on the knowledge and expertise on this topic significantly.
