Dephosphorylation of bovine casein by milk alkaline phosphatase

J Dairy Res. 1976 Feb;43(1):19-26. doi: 10.1017/s0022029900015557.

Abstract

The pH of optimum activity of alkaline phosphatase from cow's milk depended on the substrate, being 10-1 for rho-nitrophenylphosphate, 8-6 for phosphoserine, 8-0 for phosvitin and 6-8 for casein. Individual casein components were dephosphorylated more rapidly than mixtures of alphas- and beta-caseins or of alphas-, beta-and kappa-caseins and micellar casein. Mixtures of 2 components involving kappa-casein were more readily dephosphorylated than alphas- and beta-casein mixtures. At pH 6-8, lactose, whey proteins and phosphate ions had an inhibitory effect. beta-Lactoglobulin had an inhibitory effect only when the pH of the reaction was lower than the optimum pH value of the enzyme. Mg2+ and Zn2+ were not inhibitory. The optimum conditions for dephosphorylation of casein are described.

MeSH terms

  • Alkaline Phosphatase / antagonists & inhibitors
  • Alkaline Phosphatase / metabolism*
  • Animals
  • Caseins / metabolism*
  • Cattle
  • Hydrogen-Ion Concentration
  • Lactoglobulins / pharmacology
  • Magnesium / pharmacology
  • Milk / enzymology*
  • Phosphates / metabolism
  • Zinc / pharmacology

Substances

  • Caseins
  • Lactoglobulins
  • Phosphates
  • Alkaline Phosphatase
  • Magnesium
  • Zinc