Serine protease inhibitor that also shows protective effect in a cytotoxicity model. It binds to all proteases tested (trypsin (Ki=52 nM), alpha-chymotrypsin, cathepsin G, kallikrein, and human neutrophil elastase). It significantly increases neuroblastoma cell viability in an in vitro neurotoxicity model (in which cytotoxicity is induced by 6-hydroxydopamine (6-OHDA)) being a consequence of an effective decrease of reactive oxygen species (ROS) level in the cells. Does not show activity on all potassium channel tested (Kv1.1/KCNA1, Kv1.2/KCNA2, Kv1.3/KCNA3, Kv1.4/KCNA4, Kv1.5/KCNA5, Kv1.6/KCNA8, Shaker IR, and Kv11.1/KCNH2/ERG1). Belongs to the venom Kunitz-type family. Sea anemone type 2 potassium channel toxin subfamily.