Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/9/1996
Publication Date: N/A
Technical Abstract: During malting and mashing, much of the barley storage protein must be hydrolyzed. There are nearly 50 endoproteinases in germinated barley (green malt) and many of these are involved in the hydrolysis. Cysteine class endoproteinases are particularly important in hydrolyzing protein during malting. It became obvious to us that there were compounds in barley that inhibited some of the endoproteinases. Such compounds could affect protein hydrolysis, so we are studying their biochemical characteristics. We have purified and studied two low MW proteins that inhibit a crude enzyme extract prepared from green malt. Inhibitors occur in both ungerminated barley seeds and in kilned malt. The inhibitory compounds extracted from ungerminated barley are readily separated into three inhibitory fractions, with two of the three fractions apparently containing more than one inhibitor. Malt while accommodating more total inhibitory activity than barley, seems to lack one of the three inhibitor fractions. Two inhibitors have been purified from barley seeds and have been partially characterized. Our studies indicated that one of these was identical with the product of a previously studied barley aleurone gene. This protein is now known as LTP2. The other inhibitor is a protein called LTP1. Both inhibitors specifically restrict the activities of the cysteine class endoproteinases. The inhibitors may play an important role in regulating protein degradation. If these inhibitors are located in con- junction with cysteine proteinases, they could control their activities. Even if these inhibitors are separated from the endoproteinases during malting, both the enzymes and inhibitors dissolve into the wort during mashing, where they could regulate protein solubilization during mashing.