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Journal of Dairy Science Vol. 41 No. 1 13-27
© 1958 by American Dairy Science Association ®
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Separation, Concentration, and Properties of Alpha-Amylase from Cows' Milk1

E. J. Guy2 and Robert Jenness

Department of Agricultural Biochemistry, University of Minnesota, St. Paul

ABSTRACT

The presence in milk of {alpha}-amylase was confirmed. Analyses for the enzyme in milk and fractions thereof were made by measuring the rate of decrease in viscosity of starch paste with Ostwald viscosimeters. Analysis of milk and that dialyzed with various added salts revealed that the enzyme requires both calcium and chloride for activity. When milk proteins were fractionated, much of the {alpha}-amylase activity was concentrated into the lactoglobulin fraction precipitated from whey at 43% saturation with (NH4)2SO4. The enzyme was further concentrated by dissolving the lactoglobulin in a solvent consisting of ethylene glycol, ethanol, and water in the ratio of 15:29:56 by volume, adsorbing it upon rice starch and eluting with saturated CaSO4 solution. A preparation with 30 times the specific activity of lactoglobulin and containing 20% of the total activity of the lactoglobulin from which it was prepared, had starch liquefying, dextrinizing, and saccharifying properties. The optimum pH for the enzyme was 7.4 at 34° C. The energy of activation of the catalyzed reaction, measured by starch liquefaction, was 8,500 calories per mole. The enzyme was progressively inactivated by 30-min. heating between 45 and 52° C. at pH 6.4. A plot of velocity vs. velocity/substrate concentration was linear, indicating a single enzyme entity.

FOOTNOTES

1 Paper No. 3710, Scientific Journal Series, Minnesota Agricultural Experiment Station. The data for this paper are taken from a thesis presented by E. J. Guy in partial fulfillment of the requirements for the Ph.D. degree, June, 1955.

2 Present address, International Milling Company, Minneapolis, Minnesota.






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Copyright © 1958 by the American Dairy Science Association ®.