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Characterisation of the proteolytic enzymes in ungerminated and germinated rye grain. K. BRIJS (1)
and J. A. Delcour (1). Laboratory of Food Chemistry, Katholieke Universiteit Leuven.
Endoproteolytic, exoproteolytic, carboxypeptidase, aminopeptidase
and N-a-benzoyl-arginine-p-nitroanilide hydrolysing activities were detected in ungerminated and
germinated Humbolt rye whole meal, extracted with 0.05 M sodium acetate buffer (pH 5.0). During rye
grain germination, the proteolytic activity increases strikingly due to the synthesis and secretion of
endoproteases. Activities in rye germinated for 3 days are about 5.0 times higher than in ungerminated rye.
Whereas the four proteinase classes (serine-, cysteine-, metallo and aspartic-proteinases) were present in rye
germinated for 3 days, aspartic proteinases were clearly the most abundant class in ungerminated rye.
Pepstatin A, an inhibitor of aspartic proteases, reduced ca. 88% and 75% respectively of the hemoglobin
and azocasein hydrolysing activities of the proteases present in ungerminated rye. The rye proteinases are
able to degrade both wheat and rye storage proteins as shown by a release of free a-amino nitrogen as a
function of time and by characterisation of the digested proteins with SDS-PAGE.
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