Biochem J. 2011 Aug 10. [Epub ahead of print]
Overexpression of a cytosolic pyrophosphatase (TgPPase) reveals a regulatory role of pyrophosphate in glycolysis for Toxoplasma gondii
Pace DA, Fang J, Cintrón R, Docampo MD, Moreno SN
Pyrophosphate (PPi) is a critical element of cellular metabolism as both an energy donor and as an allosteric regulator of several metabolic pathways. The apicomplexan parasite, Toxoplasma gondii, uses PPi in place of ATP as an energy donor in at least two reactions: the glycolytic PPi-dependent phosphofructokinase (PFK), and the proton translocating vacuolar pyrophosphatase (V-H+-PPase). In the present work, we report the cloning, expression, and characterization of a cytosolic pyrophosphatase from T. gondii (TgPPase). Amino acid sequence alignment and phylogenetic analysis indicates that the gene encodes a family I soluble PPase. Overexpression of the enzyme in extracellular tachyzoites led to a 6-fold decrease in the cytosolic concentration of PPi relative to RH wild type tachyzoites. Unexpectedly, this subsequent reduction in pyrophosphate was associated with a higher glycolytic flux in the overexpressing mutants as evidenced by higher rates of proton and lactate extrusion. In addition to elevated glycolytic flux, TgPPase overexpressing tachyzoites also possessed higher ATP concentrations relative to wild type, RH parasites. These results implicate PPi as having a significant regulatory role in glycolysis and potentially other downstream processes that regulate growth and cell division.
PMID:21831041[PubMed - as supplied by publisher]