Niday E, Wang C S, Alaupovic P
Biochim Biophys Acta. 1980 Mar 14;612(1):67-72. doi: 10.1016/0005-2744(80)90279-x.
Kinetic experiments described in this study were carried out with an electrophoretically and immunologically homogeneous acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) preparation isolated from human erythrocyte membranes. At low concentration of substrates, the acetylcholinesterase-catalyzed reaction follows Michaelis-Menten kinetics. In comparative studies using acetylthiocholine and acetylcholine as substrates, the corresponding Km values were 150 +/- 30 microM and 200 +/- 20 microM, respectively. At low concentrations of both substrates, Hill plots indicated the existence of either a single or multiple independent active site(w). The inhibition mechanism of acetylcholinesterase by high concentration of substrates were studied by utilizing a new kinetic parameter, delta, which allows discrimination between the competitive and uncompetitive types of substrate inhibitions (Wang, C.-S. (1977) Eur. J. Biochem. 78, 568--574). This kinetic approach provided evidence that the inhibition of acetylcholinesterase by excess substrate was effected by its interaction with multiple allosteric sites on the enzyme.
本研究中描述的动力学实验是使用从人红细胞膜中分离出的一种电泳和免疫均一的乙酰胆碱酯酶（乙酰胆碱水解酶，EC 3.1.1.7）制剂进行的。在底物浓度较低时，乙酰胆碱酯酶催化的反应遵循米氏动力学。在以乙酰硫代胆碱和乙酰胆碱为底物的比较研究中，相应的Km值分别为150±30微摩尔和200±20微摩尔。在两种底物浓度都较低时，希尔图表明存在单个或多个独立的活性位点。通过利用一个新的动力学参数δ研究了高浓度底物对乙酰胆碱酯酶的抑制机制，该参数可以区分底物抑制的竞争性和非竞争性类型（Wang, C.-S. (1977) Eur. J. Biochem. 78, 568--574）。这种动力学方法提供了证据，即过量底物对乙酰胆碱酯酶的抑制是通过其与酶上多个别构位点的相互作用实现的。
