Currier S F, Mautner H G
Proc Natl Acad Sci U S A. 1974 Sep;71(9):3355-8. doi: 10.1073/pnas.71.9.3355.
The substrate specificity of choline acetyltransferase (EC 2.3.1.6) isolated from squid ganglia was investigated. The enzyme catalyzed the acetylation of choline and aminocholine but not of homocholine. In D(2)O solution there was considerable slowing of the transacetylation reaction. Photo-oxidation in the presence of methylene blue or rose bengal rapidly inactivated the enzyme, suggesting involvement of a histidine residue in the catalytic site. It seems likely that general-base catalysis by imidazole enhances the ability of enzyme-bound choline (or ammoniumcholine) to react with a thiolester group. Attempts to isolate an acetylthio-enzyme intermediate after incubation with [(14)C]acetylcoenzyme A were unsuccessful. A possible mechanism for the action of choline acetyltransferase is proposed.
对从鱿鱼神经节分离出的胆碱乙酰转移酶(EC 2.3.1.6)的底物特异性进行了研究。该酶催化胆碱和氨基胆碱的乙酰化反应,但不催化高胆碱的乙酰化反应。在重水溶液中,转乙酰化反应显著减慢。在亚甲蓝或孟加拉玫瑰红存在下进行光氧化会使该酶迅速失活,这表明催化位点中存在组氨酸残基。似乎咪唑的一般碱催化增强了酶结合胆碱(或铵胆碱)与硫酯基团反应的能力。在用[¹⁴C]乙酰辅酶A孵育后试图分离乙酰硫醇酶中间体未成功。提出了胆碱乙酰转移酶作用的一种可能机制。