Figure 2

Ca²⁺ dependent generation of mono- and diphosphate nucleotides by LALP70 phosphatase activity. Crude membrane preparations containing expressed LALP70 were incubated with ³H-UTP/UTP, 500 μM Mg²⁺ and various concentration of Ca²⁺. Apyrase activity products were separated by thin layer chromatography and ³H-labeled nucleotides were detected by a thin layer radioactivity scanner. At timepoints indicated cpm of each peak were counted and are given as percentage of all counted cpm. Mean values from three separate measurements are given. While dephosphorylation of ³H-UTP by LALP70 is independent of the Ca²⁺concentration (A), dephosphorylation of ³H-UDP (B) and thereby generation of ³H-UMP (C) depends on the Ca²⁺concentration.