Bee venom contains a variety of peptide constituents that have various biological, toxicological, and pharmacological actions. However, the biological actions of secapin, a venom peptide in bee venom, remain largely unknown. Here, we provide the first evidence that the Asiatic honeybee (Apis cerana) secapin (AcSecapin-1) exhibits anti-fibrinolytic, anti-elastolytic, and anti-microbial activities. AcSecapin-1 functions as a serine protease inhibitor-like peptide that has inhibitory effects against plasmin, elastases, microbial serine proteases, trypsin, and chymotrypsin. Consistent with these functions, AcSecapin-1 inhibited the plasmin-mediated degradation of fibrin to fibrin degradation products, thus indicating the role of AcSecapin-1 as a clotting factor. AcSecapin-1 also inhibited both human neutrophil and porcine pancreatic elastases. Furthermore, AcSecapin-1 exhibited anti-microbial activity against fungi and Gram-positive and Gram-negative bacteria. Taken together, our data demonstrated that AcSecapin-1 has a multifunctional role as an anti-fibrinolytic agent, an anti-elastolytic agent, and an anti-microbial peptide, and our data suggested novel functions for the biological actions of the bee venom peptide, secapin.

Inhibitor cysteine knot (ICK) peptides exhibit ion channel blocking, insecticidal, and antimicrobial activities, but currently, no functional roles for bee-derived ICK peptides have been identified. In this study, a bee (Apis cerana) ICK peptide (AcICK) that acts as an antifungal peptide and as an insecticidal venom toxin was identified. AcICK contains an ICK fold that is expressed in the epidermis, fat body, or venom gland and is present as a 6.6-kDa peptide in bee venom. Recombinant AcICK peptide (expressed in baculovirus-infected insect cells) bound directly to Beauveria bassiana and Fusarium graminearum, but not to Escherichia coli or Bacillus thuringiensis. Consistent with these findings, AcICK showed antifungal activity, indicating that AcICK acts as an antifungal peptide. Furthermore, AcICK expression is induced in the fat body and epidermis after injection with B. bassiana. These results provide insight into the role of AcICK during the innate immune response following fungal infection. Additionally, we show that AcICK has insecticidal activity. Our results demonstrate a functional role for AcICK in bees: AcICK acts as an antifungal peptide in innate immune reactions in the body and as an insecticidal toxin in venom. The finding that the AcICK peptide functions with different mechanisms of action in the body and in venom highlights the two-pronged strategy that is possible with the bee ICK peptide.

Toxic peptides from hornet venom, mastoparan and mastoparan-B were synthesized using the solid phase peptide synthesis method and investigated the interaction of them with phospholipid bilayer, antibacterial activity, and hemolytic activity. Both toxic peptides could induce dye release at a low concentration in neutral liposome. The binding affinity of mastoparan-B for neutral liposome was smaller than that for acidic one. Mastoparan and mastoparan-B had strong antibacterial activity for gram-positive bacteria, but weak or potent activity for gram-negative ones, respectively. Mastoparan and mastoparan-B lysed erythrocyte very little up to 5 μM.