Figure 5

cis-UCA inhibits phosphatase activity in 5637 bladder carcinoma cells. To measure the effect of cis-UCA on phosphatase activity, the 5637 cells were treated with 0.5-2% cis-UCA or phosphatase inhibitors, 20 nM calyculin A and 1 mM orthovanadate (Na₂VO₄), at pH 6.5 for 2 h. The cells were subsequently lysed, incubated with the substrate peptide for Ser/Thr phosphatase 2A (RRA(pT)VA; A.), or Tyr phosphatases (END(pY)INASL; B. and DADE(pY)LIPQQG; C.) for 30 min, and the absorbance was measured 20 min after the end of the substrate reaction (Mean ± SD; n = 3; Student's t-test * p < 0.05, ** p < 0.01, *** p < 0.001). Ser/Thr phosphatase 2A activity (A.) was measured in a reaction buffer without MgCl₂ to inhibit phosphatase 2C activity.