Main content area

Antimicrobial activity of a honeybee (Apis cerana) venom Kazal-type serine protease inhibitor

Kim, Bo Yeon, Lee, Kwang Sik, Zou, Feng Ming, Wan, Hu, Choi, Yong Soo, Yoon, Hyung Joo, Kwon, Hyung Wook, Je, Yeon Ho, Jin, Byung Rae
Toxicon 2013 v.76 pp. 110-117
Apis cerana, Bacillus subtilis, Bacillus thuringiensis, Beauveria bassiana, Escherichia coli, Fusarium graminearum, Gram-positive bacteria, antibacterial properties, antifungal properties, cysteine, elastase, entomopathogenic fungi, honey bees, peptidase K, plasmin, proteinase inhibitors, subtilisin, t-plasminogen activator, threonine, thrombin, trypsin, venoms
Insect-derived Kazal-type serine protease inhibitors exhibit thrombin, elastase, plasmin, proteinase K, or subtilisin A inhibition activity, but so far, no functional roles for bee-derived Kazal-type serine protease inhibitors have been identified. In this study, a bee (Apis cerana) venom Kazal-type serine protease inhibitor (AcKTSPI) that acts as a microbial serine protease inhibitor was identified. AcKTSPI contained a single Kazal domain that displayed six conserved cysteine residues and a P1 threonine residue. AcKTSPI was expressed in the venom gland and was present as a 10-kDa peptide in bee venom. Recombinant AcKTSPI Kazal domain (AcKTSPI-Kd) expressed in baculovirus-infected insect cells demonstrated inhibitory activity against subtilisin A (Ki 67.03 nM) and proteinase K (Ki 91.53 nM), but not against α-chymotrypsin or trypsin, which implies a role for AcKTSPI as a microbial serine protease inhibitor. However, AcKTSPI-Kd exhibited no detectable inhibitory effects on factor Xa, thrombin, tissue plasminogen activator, or elastase. Additionally, AcKTSPI-Kd bound directly to Bacillus subtilis, Bacillus thuringiensis, Beauveria bassiana, and Fusarium graminearum but not to Escherichia coli. Consistent with these findings, AcKTSPI-Kd showed antibacterial activity against Gram-positive bacteria and antifungal activity against both plant-pathogenic and entomopathogenic fungi. These findings constitute molecular evidence that AcKTSPI acts as an inhibitor of microbial serine proteases. This paper provides a novel view of the antimicrobial functions of a bee venom Kazal-type serine protease inhibitor.