Immunological comparison of (1→3,1→4)-β-glucan endohydrolases in germinating cereals

Abstract

The levels of (1→3,1→4)-β-glucanases (EC 3.2.1.73) in germinating cereal grains have been compared and the enzymes further examined using antibodies against the barley (1→3,1→4)-β-glucanase isoenzyme I. In extracts of germinating barley and rice, enzyme activity was relatively high. Significant activity was detected in wheat, rye, triticale and oats, while low levels were present in maize, sorghum and millet. Proteins in the extracts were separated by sodium dodecyl/sulphate polyacrylamide gel electrophoresis, transferred to nitrocellulose paper and probed with the polyclonal antibodies. These antibodies reacted strongly with proteins of M r 28,000 in wheat, triticale, rye, barley and oats. In barley and sorghum extracts, proteins of M r 30,000 were also recognised by the antibodies, but this protein was low in abundance or absent in the other cereals. The antibodies reacted with a protein of M r 48,000 in maize but failed to bind to any proteins in millet extracts. Although high levels of (1→3,1→4)-β-glucanase activity were detected in germinating rice, the antibodies reacted only very weakly with proteins in rice extracts, suggesting significant aminoacid sequence differences between the barley and rice enzymes.