Canziani G A, Seki C, Vidal J C
Acta Physiol Pharmacol Latinoam. 1985;35(2):165-80.
Neuromuscular blockage at the presynaptic level is the main biological effect exerted by crotoxin, the major toxin from Crotalus durissus terrificus venom. This effect requires the dissociation of this complex at the target membrane in spite of its tightness and stability under physiological conditions of pH, ionic composition and temperature. Complex dissociation should be determined by a specific set of physicochemical conditions prevailing at the neuromuscular junction. In this regard, we have studied the effect of acetylcholine on the stability of the crotoxin complex, since this effector is present at relatively high concentrations near the presynaptic membrane of the neuromuscular junction. Evidences arising from spectrofluorometric measurements, changes in enzymatic activity and crotoxin B inactivation by b-bromophenacyl bromide indicate that acetylcholine is indeed able to promote complex dissociation at neutral pH values, apparently by titration of 2-3 carboxylate groups in crotoxin A. This effect may, at least in part, contribute in determining the target specificity of this toxin.
突触前水平的神经肌肉阻滞是矛头蝮蛇（Crotalus durissus terrificus）毒液中的主要毒素——响尾蛇毒素（crotoxin）发挥的主要生物学效应。尽管该复合物在生理条件下的pH值、离子组成和温度下具有紧密性和稳定性，但这种效应需要该复合物在靶膜上解离。复合物的解离应由神经肌肉接头处存在的一组特定物理化学条件决定。在这方面，我们研究了乙酰胆碱对响尾蛇毒素复合物稳定性的影响，因为这种效应物在神经肌肉接头突触前膜附近以相对较高的浓度存在。荧光光谱测量、酶活性变化以及β-溴苯甲酰溴对响尾蛇毒素B的失活所产生的证据表明，乙酰胆碱确实能够在中性pH值下促进复合物的解离，显然是通过滴定响尾蛇毒素A中的2-3个羧基基团来实现的。这种效应可能至少部分有助于确定这种毒素的靶标特异性。
