Isolation, Toxicity and Amino Terminal Sequences of Three Major Neurotoxins in the Venom of Malayan Krait (Bungarus candidus) from Thailand

抄録

We isolated the most lethal toxins in the venom of the Malayan krait (Bungarus candidus), one of the medically most important snake species in southeast Asia. Three β-BTx like basic neurotoxins, T1-1, T1-2, and T2, with PLA₂ activity were isolated from pooled venom of eight B. candidus from southern Thailand by cation-exchange chromatography, followed by adsorption chromatography on hydroxylapatite and RPHPLC, with 14-, 16-, and 4-fold increases in toxicity compared to crude venom. The LDs₅₀ determined in mice weighing 18-20g were 0.26, 0.22, and 0.84 μg per mouse with i. v injection. T1-1 and T1-2 possessed comparable lethal toxicities to those of β1-BTx, the most toxic neurotoxin in B. multicinctus venom, and the major neurotoxin in B. flaviceps venom. The apparent molecular weights of the native toxins were approximately 25-25.5 kDa. They consist of two polypeptide chains with apparent molecular weights of 15.5-16.5 and 8-8.5 kDa, respectively. The amino terminal sequences of the two chains of each of the toxins determined by Edman degradation exhibited considerable similarity with those of the A-chains and B-chains of β-BTxs in the venom of Bungarus multicinctus.