First approach to the characterization of de novo pyrimidine biosyntheis pathway in Phytophthora infestans as a target for pathogen control

The oomycete Phytophthora infestans is the causal agent of the tomato and potato late blight, causing high economic losses worldwide. Current control strategies are far from being adequate and an interesting and unexplored alternative for control could be based on the inhibition of the de novo pyrimidine biosynthetic pathway. Indeed, inhibitors of some of the enzymes in this pathway have been proposed as therapeutic agents for a wide range of human parasites and some plant pathogens. Bioinformatic analyses of the enzymes in the P. infestans pathway were performed, in order to select the best targets for enzymatic inhibition. Based on the similarity to host enzymes, different predicted subcellular localization, architecture, predicted 3D structure and phylogenetic relations, the last two enzymes of the pathway, orotate phosphoribosyltransferase and orotidine-5-monophosphate decarboxylase, were selected as the most promising targets. Nevertheless, enzymes 3 and 4 dihydroorotase and dihydroorotase dehydrogenase cannot be ruled out. Key aspects of their metabolic inhibition were also determined for future virtual screening of a compound library using molecular docking. These enzymes are being cloned, expressed and purified in their recombinant form. This will allow their future biochemical characterization. To our knowledge, this is the first study of the pyrimidine biosynthesis in oomycetes.