The de novo purine pathway consists of ten stepwise reactions that server to convert phosphoribosyl pyrophosphate to inosine monophosphate. In general, prokaryotes tend to use freestanding single-functional enzymes for the chemical transformation, while the higher eukaryotes rely on multifunctional enzymes in this pathway. For example, human trifunctional GART catalyzes three non-sequential steps (steps 2, 3, and 5), whereas in E. coli each step is carried out by monofunctional enzymes, GARS, GAR Tfase and AIRS, in the same steps. To date, in vitro investigations of the individual enzymes have revealed much about their respective mechanism of action. There is little evidence, however, from cellular studies for the attractive hypothesis that all of these enzymes act within a multi-enzyme complex framework.

Therefore, we have investigated this pathway using chemical and molecular biology, and yeast and mammalian cell biology techniques towards our ultimate goal of an unambiguous identification and accurate delineation of a multienzyme complex in the pathway. The outcome would result in potential novel targets for drug discoveries through the identification of protein-protein associations for chemotherapeutic intervention. Moreover, it would provide a paradigm shift about the way to think cellular organizations of metabolic pathways and to consider multi-enzymatic regulatory compartments related to other cellular functions.