We searched for novel small molecules in Tityus serrulatus venom using human NEP as a screening tool.

We found a NEP-inhibiting peptide with the primary sequence YLPT, named as [des-Arg¹]-proctolin.

NEP inhibition assays showed that [des-Arg¹]-proctolin has better inhibitory activity than proctolin.

We detected NEP-like enzymes in cockroach heads homogenate using thiorphan and [des-Arg¹]-proctolin, and also by Western blot analysis.

[des-Arg¹]-proctolin may play a role in human envenomation, as well as in the paralysis and death of insects.