The kinetic constants Km app and Vmax app of phosphatase activity from a coastal tableland soil grown with orange trees, submitted to different base saturation levels (32.0; 45.0; 64.0 and 76.6%), were determined. These determinations were made in optimum pH values for alkaline and acid phosphatases and in the pH values obtained for each base saturation level. Phosphatase activity has followed Michaelis-Menten kinetics, regardless the soil base saturation levels or pH values used for enzymatic activity evaluation. Increases in the soil bases saturation resulted in lower Km app values for both enzymes, while Vmax app was increased for alkaline phosphatase and did not show significant variation for acid phosphatase. Decreases in Km app and increases in Vmax app values in response to increasing soil bases saturation were also observed for phosphatases evaluated at pH values found at each soil base saturation level. The most remarkable changes in Km app and Vmax app in response to soil base saturation were the result of shifts in pH values.
enzymatic kinetic; enzyme; phosphatase; coastal tableland; citrus; soil base saturation; liming