Cereal Chem 39:225 - 235. | VIEW
The Mechanism of Action of Malt Beta-Glucanases. II. Separation and Characterization of Malt Endo-Beta-Glucanases.
W. W. Luchsinger. Copyright 1962 by the American Association of Cereal Chemists, Inc.
Ammonium sulfate fractionation of an extract of barley green malt yielded three fractions containing endo- beta-glucanase activity. The endo-beta-glucanase in fraction A[I] was characterized by being half- inactivated by heating for 0.7 hours at 40 C. The optimum pH for enzyme action was 4.75, and the apparent ionization constants of the active form of the enzyme suggested the involvement of aspartic acid and histidine in the active site. The endo-beta-glucanase activity in fraction A[II] was not well defined. A part of the activity was lost rapidly when the preparation was diluted with distilled water. Reduced glutathione and other compounds stabilized the enzyme. When stabilized, the pH optimum and heat stability of the enzyme(s) present in A[II] were quite similar to those for the endo-beta-glucanase present in A[III]. The endo-beta-glucanase in fraction A[III] was characterized by being half-inactivated by heating for 5.2 hours at 40 C. The optimum pH for enzyme action was 4.55. The apparent ionization constant on the acid side of the active form of the enzyme suggested the involvement of aspartic acid in the active site; the apparent ionization on the alkaline side did not fall in the ranges published for common amino acids.