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Journal of Dairy Science Vol. 75 No. 12 3394-3401
© 1992 by American Dairy Science Association ®
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Purification and Properties of Alkaline Phosphatase in the Lactating Bovine Mammary Gland

Elizabeth W. Bingham 1, Kristian Garver 1, and Doris Powlen 1

1 Agricultural Research Service, USDA, Eastern Regional Research Center, 600 East Mermaid Lane, Philadelphia, PA 19118

Alkaline phosphatase has been purified 1400-fold from homogenates of lactating bovine mammary tissue. The purification procedure included subcellular fractionation, solubilization with butanol, fractionation with acetone, chromatography on concanavalin A-Sepharose, DEAE cellulose, DEAE-Sephadex, and gel filtration on Sephadex G-200. The enzyme activity was measured with the substrate p-nitrophenylphosphate in three buffers, and the maximum rate occurred at pH 10. For maximum activity, Mg2+ was required. Substrate specificity studies at three pH values indicated that the enzyme had broad specificity. It catalyzed the hydrolysis of aliphatic and aromatic phosphates and pyrophosphates, but the phosphoprotein ß-casein was a poor substrate. Potent inhibitors of the enzyme were levamisole and sulfhydryl reagents (2-mercaptoethanol, dithiothreitol, and cysteine).

Key Words: enzymes • milk • secretion

Submitted on March 30, 1992
Accepted on July 27, 1992






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Copyright © 1992 by the American Dairy Science Association ®.