When Poecilobdella manillensis attacks its prey, the prey bleeds profusely but feels little
pain. We and other research teams have identified several
anticoagulant molecules in the saliva of P. manillensis, but the substance that produces the paralyzing effect in P. manillensis is not known. In this study, we successfully isolated, purified, and identified a
serine protease inhibitor containing an
antistasin-like domain from the salivary secretions of P. manillensis. This
peptide (named poeciguamerin) significantly inhibited
elastase activity and slightly inhibited FXIIa and
kallikrein activity, but had no effect on FXa,
trypsin, or
thrombin activity. Furthermore, poeciguamerin exhibited
analgesic activity in the foot-licking and tail-withdrawal mouse models and
anticoagulant activity in the FeCl3-induced
carotid artery thrombosis mouse model. In this study, poeciguamerin was found to be a promising
elastase inhibitor with potent
analgesic and antithrombotic activity for the inhibition of
pain and
thrombosis after surgery or in inflammatory conditions.