Isolation and pharmacological characterization of a new cytotoxic L-amino acid oxidase from Bungarus multicinctus snake venom

Ethnopharrnacological relevance: Bungarus multicinctus snake belongs to Elapidae family and is widely distributed in southern China. It is widely used in traditional Chinese medicine with the effect of dispelling wind and removing obstruction in the meridians. Moreover, it is also as a chief ingredient of many polyherbal formulations for the treatment of cancer. Aim of the study: To evaluate the antitumor activity of Bungarus multicinctus snake venom components and isolate, characterize the most effective anti-tumor component of Bungarus multicinctus snake venom. Materials and methods: The in vitro antitumor activity of Bungarus multicinctus venom components was detected by cytotoxicity assay and cell apoptosis assay. A unique LAAO from Bungarus multicinctus venom named as BMA-potxin was isolated and characterized by Sephadex G-75 gel filtration, Sephadex G-25 desalting, Q ion-exchange chromatography and subsequent amino acids sequence determination. The LAAO activity and enzyme kinetics of BM-Apotxin was detected by microplate assay. Results: BM-Apotxin, a 65KDa glycoprotein, which contributed to the most anti-tumor effects of Bungarus multicinctus venom. BM-Apotxin can selectively kill tumor cells, with less cytotoxicity to the normal cells. BM-Apotxin is an L-amino acid oxidase (LAAO) with high sequence identity to other snake venom LAAOs. Its anti-tumor activity is mainly due to the hydrogen peroxide produced from LAAO oxidation. But the catalase did not reverse its anti-tumor effect completely. Like other snake venom LAAOs, BM-Apotxin can oxidize many L amino acids, not D amino acids. The optimum substrate for BM-Apotxin is L-Phe. Moreover, BM-Apotxin deglycosylation can significantly reduce the LAAO activity and anti-tumor activity of BM-Apotxin. Conclusion: This study will facilitate the study on anti-tumor mechanism of snake venom and drug development based on Bungarus multicinctus venom.