Alkaline phosphatase (AP) activity was measured as previously described [15 (
link),16 (
link)] with some modifications. Caco-2 cells were treated with or without 2 mM IIAEK. Micelles were prepared as previously described [13 (
link)]. Following treatment, the cells were washed twice with 0.9% NaCl. Subsequently, 691 μL of cold 50 mM Tris buffer [pH 7.5,
Trizma base (Sigma-Aldrich, St. Louis, MO, USA, T1503)] was added. Protein was collected on ice and homogenized with an injection needle (26G × 1/2) (TERUMO, Tokyo, Japan,
NN-2613S). AP activity was estimated using 1.25 mg/mL disodium p-nitrophenol phosphate as a substrate in Tris-HCl buffer [pH 10.0, 5 mM MgCl
2.
6H
2O (Wako, 135-00165) and 200 mM
Trizma base (Sigma-Aldrich, St. Louis, MO, USA, T1503)]. After 30 min of incubation at 37 °C, the absorbance at 405 nm was measured, and AP activity was calculated as μmol/min using a calibration curve for various concentrations of p-nitrophenol. μmol/min was defined as U. U was converted to U/mg protein in order to normalize AP activity to the protein concentration, which was determined using a commercially available kit (BioRad,
protein assay; BioRad).
Takeuchi A., Hisamatsu K., Okumura N., Sugimitsu Y., Yanase E., Ueno Y, & Nagaoka S. (2020). IIAEK Targets Intestinal Alkaline Phosphatase (IAP) to Improve Cholesterol Metabolism with a Specific Activation of IAP and Downregulation of ABCA1. Nutrients, 12(9), 2859.