Use of N-methyl-D-glucamine as buffer in the determination of serum alkaline phosphatase activity

We describe a method for determining serum alkaline phosphatase activity with use of N-methyl-D-glucamine buffer, Na+ is a definite activator, whereas NH4+ and Li+ inhibit enzyme activity. Optimum reaction conditions are: methylglucamine buffer, 0.35 mol/L, pH 10.2 +/- 0.1 (30 degrees C); NaCl, 70 mmol/L; MgCl2, 0.5 mmol/L; disodium 4-nitrophenyl phosphate, 15 mmol/L; reaction temperature, 30 degrees C; reaction time, 2 min. The assay conditions are optimum for all human serum isoenzymes.