FIGURE 5.

SPN lacks cADPR hydrolysis and cyclase activity. A, analysis of cADPR hydrolase activity. Shown are HPLC chromatograms of the products generated by incubation of the various proteins indicated in the Fig. with 1 mm cADPR for 1 h (recombinant CD38) or for 6 h (all other proteins shown). Locations of the peaks representing cADPR and ADPR are shown at the top. Note that commercially obtained cADPR contained some ADPR, as shown in the chromatogram lacking enzyme. B, cycling assay to measure cADPR synthesis. Shown are plots of resorufin fluorescence over time generated from the indicated standard concentrations of cADPR used as reference standards (cADPR Stds) or from cADPR synthesized by enzymatic reactions conducted with the proteins listed in the Fig. Data shown are from a single experiment representative of at least three independent experiments with identical results.