Submitted to: Cereal Foods World
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2000
Publication Date: N/A
Technical Abstract: During oat seed germination, the insoluble endosperm storage proteins must be hydrolyzed and transported to the embryo for use of the developing plantlet until it can take care of its own needs. We showed earlier that pH 6.2-active serine and metalloproteinases were the predominant gelatin-hydrolyzing enzymes of oats, while the oat globulins were degraded by pH 3.8-active cysteine proteases. The pH of the endosperms of germinating oats is 6.2. Avenins, one group of oat storage proteins, are prolamins with 22-33 kD MWs. This study continues our characterization of the germinated oat proteinases by determining which hydrolyze the avenins. Avenins of resting oat seeds were purified and hydrolyzed with proteinases that were extracted from oat seeds that were germinated for various periods. The peptides released were analyzed using SDS-PAGE. The alpha-avenins were hydrolyzed at pH 3.8 by cysteine proteinases from 4-day germinated seeds. In contrast, the beta-avenins were hydrolyzed by similar enzymes that were active only after 8 days of germination. At pH 6.2 or pH 5.0 the avenins were not degraded by any of the germinated oats endoproteinases. Based on the results of this study and our earlier results, it is probable that some kind of pH compartmentalization occurs within the oat seed during germination. It appears that after four days of germination either new proteinases form or that some preexisting proteinases are activated. Such activation could involve cysteine proteinase inhibitors. The cysteine proteinases are apparently responsible for the majority of the storage protein hydrolysis that occurs during oat germination.