Proteins that inhibit a-amylases have been isolated from plants and microorganisms. These inhibitors can have natural roles in the control
of endogenous a-amylase activity or in defence against pathogens and pests; certain inhibitors are reported to be antinutritional factors. The
a-amylase inhibitors belong to seven different protein structural families, most of which also contain evolutionary related proteins without
inhibitory activity. Two families include bifunctional inhibitors acting both on a-amylases and proteases. High-resolution structures are
available of target a-amylases in complex with inhibitors from five families. These structures indicate major diversity but also some
similarity in the structural basis of a-amylase inhibition. Mutational analysis of the mechanism of inhibition was performed in a few cases
and various protein engineering and biotechnological approaches have been outlined for exploitation of the inhibitory function.