Submitted to: Journal of the American Society of Brewing Chemists
Publication Type: Abstract Only
Publication Acceptance Date: 2/5/1996
Publication Date: N/A
Technical Abstract: The endosperm tissue of germinated barley (Hordeum vulgare L. Cv Morex') seeds contains a relative high level of aspartic endopeptidase activity. This localization made it seem likely that these enzymes could hydrolyze some of the endosperm proteins. We have now purified three aspartic class endopeptidases from germinated barley. All three enzymes had similar pH activity optima (pH 3.5 to 4.5) and pI values (around 4.5), while their molecular sizes ranged from 30 kD to 50 kD. The purified aspartic proteinases selectively digested a group of barley seed proteins that have been postulated to serve as defensive proteins and which are coded by the alpha-amylase/trypsin inhibitor' super gene family. Each enzyme appeared to consist of two or more subunits, and all of the subunits cross-reacted with antiserum raised against an aspartic proteinase previously purified from barley seed. It thus appears that these proteinases from green malt are closely related to the aspartic proteinase from ungerminated seed.