The damage caused by Anticarsia gemmatalis motivates this study on the insect's adaptive mechanisms to soybean. The lipoxygenase pathway produces and releases jasmonic acid, involved in the regulation of the plant defense genes which encodes protease inhibitors (PI) production. Three soybean cultivars IAC-18, IAC-24 and Foscarin-31 were sprayed with water and berenil, a synthetic inhibitor, at 0.60 and 1.0% (w/v) and then infested with A. gemmatalis larvae. The lipoxygenase (LOX) activity increased in the leaves of Foscarin-31, IAC-18 and IAC-24 by 87%, 81% and 78%, respectively after 24h of A. gemmatalis damage. The IAC-18 revealed the lowest increase in PI when compared with the other cultivars. Protease, amidase and esterase activity in soybean larvae dropped drastically after berenil application. Protease inhibitors may be included in the control strategies of A. gemmatalis in soybean by lowering the digestive enzymes activity in the larval midgut, thus affecting insect growth and development.