Talesa V, Grauso M, Giovannini E, Rosi G, Toutant J P
Department of Experimental Medicine, University of Perugia, Italy.
Neurochem Int. 1995 Aug;27(2):201-11. doi: 10.1016/0197-0186(95)00006-t.
Transverse sections of Octopus tentacles were stained for acetylcholinesterase (AChE) activity. An intense staining, that was suppressed by preincubation in 10(-5) M eserine, was detected in a number of neuronal cells, nerve fibres and neuromuscular junctions of intrinsic muscles of the arm. Octopus acetylcholinesterase was found as two molecular forms: an amphiphilic dimeric form (G2) sensitive to phosphatidylinositol phospholipase C and a hydrophilic tetrameric (G4) form. Sequential solubilization revealed that a significant portion of both G2 and G4 forms was recovered only in a high salt-soluble fraction (1 M NaCl, no detergent), Heparin (2 mg/ml) was able to solubilize G2 and G4 forms with the same efficiency than 1 M NaCl. The solubilizing effect of heparin was concentration-dependent and was reduced by protamine (2 mg/ml). This suggests that heparin operates through the dissociation of ionic interactions existing in situ between globular forms of AChE and cellular or extracellular polyanionic components. Interaction of AChE molecular forms with heparin has been reported so far in only a few instances and its physiological meaning is uncertain. G2 and G4 forms, interacting or not with heparin, all belong to a single pharmacological class of AChE. This suggests the existence of a single AChE gene. Amphiphilic and hydrophilic subunits thus likely result either from the processing of a single AChE transcript by alternative splicing (as in vertebrate AChE) or from a post-translation modification of a single catalytic peptide.
对章鱼触手的横切片进行乙酰胆碱酯酶（AChE）活性染色。在臂部固有肌的许多神经细胞、神经纤维和神经肌肉接头中检测到强烈染色，该染色可被10⁻⁵ M毒扁豆碱预孵育所抑制。章鱼乙酰胆碱酯酶有两种分子形式：一种对磷脂酰肌醇磷脂酶C敏感的两亲性二聚体形式（G2）和一种亲水性四聚体（G4）形式。连续增溶显示，G2和G4形式的很大一部分仅在高盐可溶部分（1 M NaCl，无去污剂）中回收，肝素（2 mg/ml）能够以与1 M NaCl相同的效率增溶G2和G4形式。肝素的增溶作用是浓度依赖性的，并被鱼精蛋白（2 mg/ml）降低。这表明肝素通过解离AChE球状形式与细胞或细胞外多阴离子成分之间原位存在的离子相互作用来发挥作用。迄今为止，仅在少数情况下报道了AChE分子形式与肝素的相互作用，其生理意义尚不确定。与肝素相互作用或不相互作用的G2和G4形式均属于AChE的单一药理学类别。这表明存在单一的AChE基因。因此，两亲性和亲水性亚基可能要么是由单一AChE转录本通过可变剪接加工而成（如在脊椎动物AChE中），要么是由单一催化肽的翻译后修饰产生。
