Post-Translational Modifications of β-Amylases during Germination of Wheat and Rye Seeds

Abstract

β-amylase processing during the germination of cereal seeds was investigated in one cultivar of wheat and one cultivar of rye by means of immunoprecipitation techniques, isoelectric focusing including a specific immunoelimination of α-amylases, western blotting and immunoaffinity chromatography combined with two-dimensional electrophoresis. A shift of β-amylase constituents towards higher pI values previously described for germinating wheat seeds was confirmed, and similar changes were found for rye. Moreover, papaïn induced the same modifications on the free and bound forms of β-amylase in both cereals, but did not further modify the β-amylase extracted from germinated seeds. In both cereals all β-amylase constituents behaved as a single antigen which remained unchanged in regard to the reactions of immunoprecipitation after 5 days of germination. The molecular size of the enzyme is modified during germination: constituents of 63 kDa (rye) and 61, 63 and 66 kDa (wheat) in ungerminated seeds were replaced by a single molecular weight species of 57 kDa in the 5-day germinated seeds of each of the two cereals. The correspondence between the pI values and the M r of the constituents detected in ungerminated wheat seeds suggest that the processing is potentially active in resting seeds.