4.1.1. Lethality

Like other insecticidal proteins, including the widely used Cry proteins of *B. thuringiensis* [89], the "parent" proteins of Jaburetox, canatoxin and JBU, or SBU, in the case of Soyuretox, need a step of proteolytic activation to act upon insects of different orders. Even though these urease isoforms present entomotoxic effects *per se*, they are not lethal when fed to insects with trypsin-based digestion [35]. This caveat can be surpassed by employing Jaburetox as first demonstrated by Mulinari et al. [57]. Since that finding, several species were tested for lethality and almost all of them were susceptible to Jaburetox. This peptide was effective via injection and oral administration against juveniles and adults. Moreover, the doses employed were very low when compared to other entomotoxic proteins derived from plants [35]. There are less information available for Soyuretox, although the effect of a dose comparable to those employed with Jaburetox also resulted lethal in *D. peruvianus* [64]. The only exception to this trend so far has been the cockroach *Nauphoeta cinerea*, since feeding or injecting Jaburetox did not result in mortality [86]. As we will discuss later, the effect on the activities of the central nervous system enzymes was different in cockroaches of this species when compared to susceptible insects such as the kissing bug *R. prolixus*. This difference could explain, at least in part, the resistant phenotype of *N. cinerea*.
