Inhibitor of cathepsin D (aspartic protease) and trypsin (serine protease). Protects the plant by inhibiting proteases of invading organisms. In tubers and green buds of untreated plants. After abscisic acid treatment or mechanical wounding is mostly accumulated in leaves, to a lesser extent in stems, but not in roots. By abscisic acid (ABA), jasmonic acid (JA) and wounding. Belongs to the protease inhibitor I3 (leguminous Kunitz-type inhibitor) family.