Table II.

Effects of inhibitors on AP activities of PM NPA-binding proteins

SubstrateControl SANPA (50 μm)EGTA (2 mm)PMSF (100 μm)Bestatin (20 μm)Amastatin (20 μm)Apstatin (20 μm)Puromycin (20 μm)PAQ22 (20 μm)Dithiothreitol (DTT; 5 mm)Vanadate (5 mm)Thiorphan (50 μm)
nmol min−1 mg−1 %
Tyr-AFC381 ± 17.5655878417253614810895101
Ala-Pro-AFC71 ± 7.77684718487268798699397
Ala-AFC89 ± 5.35420873637945334969798
Pro-AFC44 ± 9.28179795888616699739097

Proteins from NPA affinity fractions II and III (Fig. 1D) were reconstituted by dialysis in AP assay buffer, then assayed fluorometrically for AP activity with AFC conjugates (20 μm) in the presence or absence of inhibitors. Values shown for inhibitor assays are percent control-specific activities (SA). Values calculated are derived from means and sd of three independent experiments. Table entries marked with an asterisk were significantly different from their control (P < 0.05) when analyzed by Student-Newman-Keuls ANOVA.