CD38 enzymatic activities are independent of signaling properties. Production of cADPR was assayed in a panel of normal B cells and cell lines using a radioreceptor assay. Results are presented as picomoles of cADPR produced in 30 minutes. The cells are divided in signaling and nonsignaling as inferred from the experiments described in Figure 4C. U266 and K562 are CD38^low/− and were used as control. Error bars represent standard deviation derived from 3 independent measurements.