Alkaline Phosphatase (ALP)

  • Enzymes for Clinical Chemistry

The enzyme is widely used as a marker in ALP based immunoassay.

Origin calf intestinal mucosa
Systematic name

Orthophosphoric-monoester phosphohydrolase (alkaline optimum)

EC Number
Reaction formula

An orthophosphoric monoester + H2O →→→ An alcohol + Orthophosphate


Appearance clear and almost colorless liquid
Activity ≧100,000 DEA U/mL
Specific activity ≧6,000 DEA U/mg protein
Protein 10–20 mg protein/mL, Biuret
Stabilizer glycerol
Storage condition at 2∼7℃ (do not freeze)


Molecular weight ca. 140 kDa (gel filtration)
pH Optimum 9.5–10.0
pH Stability 6.5–11.0
Optimum temperature 50℃
Thermal stability below ca. 40℃
Stability (liquid form) stable at 37℃ for at least four weeks
Stability (liquid form) stable at 5℃ for at least two years
Activators Mg2+, Tris buffer, diethanolamine
Inhibitors inorganic phosphate, ethylenediaminetetraacetic acid (EDTA)


The enzyme is widely used as a marker in ALP based immunoassay.


  • O’Sullivan, M. J. et al., Anal. Biochem., 100, 100–108 (1979).
  • Bergmeyer, H. U., “Methods of Enzymatic Analysis,” Vol. 2 (3rd ed.), Verlag Chemie, Weinheim, Germany, 1983, pp. 269–270.
  • Crowther, J. R., “ELISA: Theory and Practice,” Humana Press, New York, 1995.
  • Price, C. P. and Newman, D. J., “Principles and Practice of Immunoassay,” Macmillan Press, London, 1997.