Docherty M, Bradford H F
Department of Biochemistry, Imperial College of Science and Technology, South Kensington, London SW7 2AY, U.K.
Neurochem Int. 1988;13(1):119-27. doi: 10.1016/0197-0186(88)90111-8.
Choline acetyltransferase activity was detected in extensively washed membranes prepared from rat and guinea pig synaptosomes. When these preparations were treated with the non-ionic detergent Triton X-114 and heated to 37 degrees C to cause phase separation, a significant percentage was found to associate with the detergent-rich phase, indicating that the enzyme might be an integral membrane-bound protein. In guinea pigs receiving septal lesions, a large reduction in both total and in Triton X-114-extractable choline acetyltransferase in hippocampal synaptosomes was observed indicating that the detergent-extracted form is associated with cholinergic nerve terminals. When membrane-bound choline acetyltransferase from lysed, washed synaptosomes was incubated in Triton X-114, 30% of the membrane-associated enzyme could be extracted into the detergent-rich phase. This extraction could be improved by reducing the chloride content of the extraction medium. When the chloride content of synaptosomes, prepared from rat cerebral cortex, was manipulated, by either exposure to ?-aminobutyric acid, muscimol or to a medium containing reduced levels of chloride, the ability of antibodies against choline acetyltransferase to specifically immunolyse (in the presence of complement) the cholinergic synaptosome population was enhanced. These results suggest that the choline acetyltransferase found in the nerve terminal region exists in at least two forms (a soluble and a lipophilic form) which are partially interconvertible. The conversion between the two forms can be influenced by chloride ions.
在从大鼠和豚鼠突触体制备的经过充分洗涤的膜中检测到了胆碱乙酰转移酶活性。当用非离子去污剂Triton X - 114处理这些制剂并加热至37摄氏度以引起相分离时，发现有相当比例的酶与富含去污剂的相相关联，这表明该酶可能是一种整合膜结合蛋白。在接受隔区损伤的豚鼠中，观察到海马突触体中总胆碱乙酰转移酶以及可被Triton X - 114提取的胆碱乙酰转移酶都大幅减少，这表明去污剂提取形式与胆碱能神经末梢相关。当将来自裂解、洗涤后的突触体的膜结合胆碱乙酰转移酶在Triton X - 114中孵育时，30%的膜相关酶可被提取到富含去污剂的相中。通过降低提取介质中的氯离子含量可改善这种提取效果。当通过暴露于γ-氨基丁酸、蝇蕈醇或含有降低水平氯离子的介质来操控从大鼠大脑皮层制备的突触体的氯离子含量时，抗胆碱乙酰转移酶抗体在补体存在下特异性免疫溶解胆碱能突触体群体的能力增强。这些结果表明，在神经末梢区域发现的胆碱乙酰转移酶至少以两种形式存在（一种可溶形式和一种亲脂形式），它们可以部分相互转化。两种形式之间的转化可受氯离子影响。
