FURTHER CHARACTERIZATION OF THE 12 KDA PROTEASE ALPHA-AMYLASE INHIBITOR PRESENT IN MAIZE SEEDS

A 12 kDa protease/alpha-amylase inhibitor was purified from maize seeds and studied. Its trypsin- and amylase-inhibitor activities against enzymes from different origins were determined, as well as its optimal pH for inhibition. Eight different proteases, extracted from insects and fungi which attack grains during storage, were tested with the inhibitor. Bovine trypsin and trypsin-like proteases from the insect P. truncatus, and the fungi A. niger and A. fumigatus, were recognized by this inhibitor. Out of 11 alpha-amylases tested, only those from T. castaneum and C. maculatus were recognized by this inhibitor. The optimal pH's for the inhibition of trypsin and the trypsin-like protease from P. truncatus were 8.0 and 7.5, respectively. The optimal pH activity was 5.0 for the inhibition of amylases from T. castaneum and C. maculatus.