FIG. 3.

Effects of yeast E-NPPs on phosphate uptake and extracellular nucleotide-derived phosphate hydrolysis. (A) Strains lacking NPP1 and/or NPP2 were evaluated for their contributions to nucleotide phosphate hydrolysis as a function of detected phosphate uptake. Extracellular [γ-³²P]ATP was utilized as a substrate, and cultures were grown over a 24-h time course in phosphate-depleted medium. A loss of either or both genes caused a defect in phosphate uptake. (B) Extracellular [α-³²P]ATP was utilized to measure phosphate hydrolysis at the proximal position. Loss of either or both genes enhanced the defect of phosphate hydrolysis; the effect was most severe in strains lacking both genes.