Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/25/2007
Publication Date: 6/25/2007
Citation: Schmitt, M., Budde, A.D., Marinac, L.A. 2007. Serine proteinases from barley malt may degrade beta-amylase. In: (Edney, M. and Izydorczyk, M.) The Science and Joy of Canadian Barley and Beer. 5th Canadian Barley Symposium, June 25-29, 2007, Winnipeg, Manitoba, Canada. p. 18.
Technical Abstract: Barley seed proteinases are critically important to seed germination and malting in that they generate amino acids from seed N reserves, supporting embryo growth during germination and yeast fermentation during brewing. However, relatively little is known regarding the endogenous protein substrate specificity of malt proteinases. Several cysteine endoproteinases have been shown to degrade Hordein, the principal barley storage protein. Other (aspartic) proteinases have been implicated in partial proteolysis during protein trafficking to storage compartments. Using a combination of zymography and Western blot analysis, we show that several barley malt serine-class endoproteinases can degrade barley beta-amylase, and that different members of the beta-amylase-degrading serine proteinases are localized in different seed tissues. The serine endoproteinases increase in activity during germination from the second day after steeping. Correlations between serine- and cysteine-class proteinase activities and common malting quality parameters suggest that the two classes of endoproteinases may have different physiological functions in the mobilization of seed reserves. This is the first identification of an endogenous substrate for malt serine endoproteinases as well as the first demonstration that malt endoproteinases may degrade enzymes performing key metabolic functions during germination.