In this work we compared two plant ureases, jackbean urease (JBU) and embryo-specific soybean urease (SBU) and a bacterial (Bacillus pasteurii) urease, for kinetic parameters and other biological properties described recently for ureases that are independent of the ureolytic activity. The insecticidal effect of ureases was investigated in feedingtrials with the cotton sucker bug,Dysdercus peruvi-anus (Hemiptera) as an insect model. Contrastingwith B. pasteuriiurease (PBU), both plant ureases presented potent insecticidal activity, with LD50 values of (w/w) and (w/w) for JBU and SBU, respectively