Alkaline phosphatase of milk. 2. Purification of the enzyme

Abstract

The alkaline phosphatase of milk was purified 5600 times compared to the initial whole milk on a protein N basis. The yield was 1.5%. An essential step in the purification procedure depends on the unique ability of butanol to disrupt the lipoprotein complex with which the phosphatase is normally associated. The final product had a specific activity of 15,300 units/mg. N (Qpl06000), estimated from hydrolysis of Na beta-glycerophosphate at 37[degree]. Comparison of the activity with a protein fraction separated electrophoretically indicated that the purified enzyme was probably homogeneous. Homogeneity was also indicated by the lack of diesterase or pyrophosphatase activity in the prepn. A red protein fraction was separated from the buttermilk during the purification. The identity of this protein was not established.