Studies on the inhibition of immobilised alkaline phosphatase by metal ions and EDTA in a flow-injection system

Inhibition of immobilized alkaline phosphatase by several metal ions and EDTA was studied in a single-channel flow-injection system. The enzyme was immobilised on controlled pore glass. The same enzyme preparation was used for three months. The inhibition by the tested compounds is reversible, the inhibitors are removed from the enzyme reactor just by passing glycine buffer. The metal ion inhibition response is linear in the range 1 × 10−4–1 × 10−6 M, while for EDTA the linearity is between 1 × 10−5–5 × 10−5 M. The relative standard deviation at mid-calibration range is below 5% in all cases. The nature of the inhibition was studied for beryllium and EDTA. Non-competitive inhibition was found at low substrate concentrations, while for substrate concentrations higher than 10−3 M inhibitor and substrate compete for the enzyme.