Studies ongoing in the laboratory are focused on the characterization of proteins with potential therapeutic value in the treatment of the trypanosome and malarial parasites. These parasites cause major pathology throughout the third world and current drug therapy is limited. In the trypanosome parasite our studies focus on polyamine and glutathione biosynthetic enzymes, including characterization of ornithine decarboxylase and S-adenosylmethionine decarboxylase, two enzymes that are essential for polyamine biosynthesis, and g-glutamylcysteine synthetase, which catalyzes the first committed step in glutathione biosynthesis. In the malarial parasite we are studying dihydroorotate dehydrogenase, a key enzyme in the de novo pyrimidine biosynthetic pathway. Although these enzymes are essential to all organisms, differences between the host and parasite metabolism can be exploited to design selectively toxic inhibitors. Our goals are to elucidate the mechanism of catalysis, the basis for substrate and cofactor specificity, and the energetic basis for subunit-subunit interactions for each enzyme. Site-directed mutagenesis, steady-state and presteady-state kinetic analysis and X-ray crystallography are key tools for these analyses. In addition regulation of these enzyme pathways is being studied in the trypanosome parasite utilizing tools such as RNAi and gene over-expression. Projects to exploit these targets for the development of new chemotherapy are also underway.
RESEARCH INTERESTS
Polyamine and glutathione biosynthetic enzymes in trypanosomes
Polyamine and glutathione biosynthetic enzymes in trypanosomes
Pyrimidine biosynthesis as a drug target in malarial parasites
Pyrimidine biosynthesis as a drug target in malarial parasites
Drug design in protozoan parasites
RECENT PUBLICATIONS
Huynh,T.T., Huynh, V.T., Harmon, M.A. and Phillips, M.A., "Gene knockdown of gamma-glutamylcysteine synthetase by RNAi in the parasitic protozoa Trypanosoma brucei demonstrates that it is an essential enzyme" J. Biol. Chem., 278:39794-39800, 2003
Baldwin, J., Michnoff, C.H., Malmquist, N.A., White, J., Roth, M.G., Rathod, P.K. and Phillips, M.A., "High-Throughput Screening for Potent and Selective Inhibitors of Plasmodium falciparum Dihydroorotate Dehydrogenase" J. Biol. Chem., 280:21847-21853, 2005
Shah, R., Akella, R, Goldsmith, E.J. and Phillips, M.A., "The X-ray structure of Paramecium bursaria chlorella virus arginine decarboxylase: insight into the structural basis for substrate specificity" Biochemistry, 46:2831-2841, Spring 2007
Willert, E.K., Fitzpatrick, R. and Phillips, M.A., "Allosteric regulation of an essential trypanosome polyamine biosynthetic enzyme by a catalytically dead homolog" Proc. Natl. Acad. Sci. USA, 104:8275-8280, Spring 2007
Rodgers, M., Albanesi, J.P. and Phillips, M.A., "Phosphatidylinositol 4-kinase type III? is required for cytokinesis and golgi formation in Trypanosoma brucei" Eukaryotic Cell, in press 2007
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