Thioredoxin in Barley: Could It Have a Role in Releasing Limit Dextrinase in Brewery Mashes?

Craig B. Heisner¹ and Charles W. Bamforth^1,2
¹ Department of Food Science and Technology, University of California, Davis, CA 95616
² Corresponding author. E-mail: cwbamforth@ucdavis.edu
A preliminary report of some of this work was presented at the American Society of Brewing Chemists meeting in Albuquerque, New Mexico in 2003.

J. Inst. Brew. 114(2), 122–126, 2008 | VIEW ARTICLE

ABSTRACT
There is not a strong correlation between the amount of thioredoxin in barley and the total protein content of the grain. The level of detectable thioredoxin decreases during germination, whereas the amount of limit dextrinase increases, for the most part in a bound form. Under no circumstances could a release of limit dextrinase in an active form be demonstrated through the agency of the thioredoxin system. By contrast the thiol agent dithiothreitol, especially in the presence of calcium, did promote the activation of limit dextrinase. Of most pronounced effect, however, was the lowering of pH. Three-fold higher limit dextrinase activity was achieved when the pH was lowered to 4.0

Key words:
Barley, limit dextrinase, pH, thioredoxin.