Stability and activity of potato acid phosphatase in aqueous surfactant media

The effect of three different classes of surfactants viz., anionic, cationic and neutral on catalytic activity of potato acid phosphatase (AcPase) was studied. Anionic surfactants bis(2-ethylhexyl) sodium sulfosuccinate (AOT) and sodium dodecyl sulfate (SDS) inhibited AcPase activity completely at 3 mM concentration. The cationic surfactant cetyltrimethylammonium bromide (CTAB), at 3.33 mM enhanced the activity by 20 per cent. Increase in CTAB concentration decreased the activity, so that only 50 per cent was retained at 27 mM concentration. Brij 35, a neutral surfactant also decreased the activity, whereas TritonX-100 had little or no effect. At low CTAB concentration, an increase in Vmax and a decrease in Km was observed and the V/K ratio increased. TritonX-100 enhanced Vmax without changing Km. The V/K ratio was also increased. The UV-difference spectra of AcPase in presence of CTAB showed perturbations. The intensity of intrinsic fluorescence also enhanced in presence of CTAB.