‘FREE’ AND ‘BOUND’ β-AMYLASES DURING MALTING OF BARLEY. CHARACTERIZATION BY TWO-DIMENSIONAL IMMUNOELECTROPHORESIS

Major qualitative and quantitative changes in the β-amylases and in other salt soluble barley proteins occurred during the first four days of germination. Two soluble forms of barley β-amylase, ‘free’ β-amylase and β-amylase aggregated with a non-active protein Z, were found in extracts from all stages. A third enzyme form appeared during malting. Immunoelectrophoretic characterization seemed to support the possibility that this enzyme form could be a product of ‘bound’ β-amylase solubilization. All soluble forms of β-amylase and of protein Z in malt were electrophoretically heterogeneous. Two different, immunochemically related forms of protein Z present after malting retained their immunoelectrophoretic properties during brewing and were found to be dominant antigens in beer.