ACP-TX-I and ACP-TX-II, Two Novel Phospholipases A2 Isolated from Trans-Pecos Copperhead Agkistrodon contortrix pictigaster Venom: Biochemical and Functional Characterization

This work reports the purification and biochemical and functional characterization of ACP-TX-I and ACP-TX-II, two phospholipases A(2) (PLA(2)) from Agkistrodon contortrix pictigaster venom. Both PLA(2)s were highly purified by a single chromatographic step on a C-18 reverse phase HPLC column. Various peptide sequences from these two toxins showed similarity to those of other PLA(2) toxins from viperid snake venoms. ACP-TX-I belongs to the catalytically inactive K49 PLA(2) class, while ACP-TX-II is a D49 PLA(2), and is enzymatically active. ACP-TX-I PLA(2) is monomeric, which results in markedly diminished myotoxic and inflammatory activities when compared with dimeric K49 PLA(2)s, confirming the hypothesis that dimeric structure contributes heavily to the profound myotoxicity of the most active viperid K49 PLA(2)s. ACP-TX-II exhibits the main pharmacological actions reported for this protein family, including in vivo local myotoxicity, edema-forming activity, and in vitro cytotoxicity. ACP-TX-I PLA(2) is cytotoxic to A549 lung carcinoma cells, indicating that cytotoxicity to these tumor cells does not require enzymatic activity.