RELEASE AND ACTIVATION OF BARLEY BETA-AMYLASE BY MALT ENDOPEPTIDASES

Cysteine-endopeptidases, purified from malt and 2-mercaptoethanol (2-ME), mediated the release and activation of bound beta-amylase prepared from quiescent barley seeds (Hordeum vulgare L. cv. Clipper). Treatment with 2-ME (1 mM) resulted in an increase in the activity of the enzyme in the soluble fraction, but there was no change in the number of isoforms identified by isoelectric focusing and activity staining using a starch overlay procedure. Treatment with two cysteine-endopeptidases prepared from germinating barley (in the presence of 1 mM 2-ME) resulted in a similar increase in activity and the generation of a range of isoforms with increased pI values. These were similar to those found in germinated barley. Two isoforms found in germinated barley were not present in the endopeptidase-treated samples, however. The activity of free beta-amylase, extracted from quiescent barley seed, was also increased by treatment with 2-ME and the endopeptidases. © 1992, Academic Press Limited. All rights reserved.