ABSTRACT
The enzyme acetylcholinesterase (AChE) is a member of a discrete family of serine hydrolases found in synaptic and non-synaptic sites. Its significant role of acetylcholine hydrolysis is observed at the synapses, whereas its role at non-synaptic sites is still ambiguous. The venom of snakes of the family Elapidae represents a non-synaptic source of AChE, and the genus Bungarus is known to have a significant quantity of the enzyme – approximately 8 mg/g of dried venom (0.8% w/w). By comparative amino acid sequence studies, snake venom AChE shows homology with the catalytic domain of cholinesterases from other sources and has a remarkable level of similarity. The range of sensitivity of venom AChEs to diverse inhibitors is similar, with the exception of fasciculin, which differs in its inhibitory action depending on the source of venom. The quantity of AChE or fasciculin in a given venom is an important determinant of its importance during envenomation, and enhanced levels of AChE and fasciculin are associated with the termination of cholinergic transmission at the prey’s neuromuscular junction as well as in the central nervous system. Moreover, the existence of the enzyme in elapid venoms, due to its monomeric structure, high catalytic activity and general similarity to synaptic AChE, facilitates experimental use in further biochemical studies.
