Breier A, Vrbanová A, Docolomanský P, Bohácová V, Ziegelhöffer A
Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Bratislava, Slovakia.
Gen Physiol Biophys. 1996 Aug;15(4):291-307.
The effects of newly synthetized derivatives of furylethylene: i) 1-(5-nitro-2-furyl)-2-phenylsulfonyl-2-furylcarbonyl ethylene (FE1), ii) 1-(5-phenylsulfonyl-2-furyl)-2-phenylsulfonyl-2-furylcarb onyl ethylene (FE2), iii) 1-(5-phenylsulfonyl-2-furyl)-2-phenylsulfonyl-2-tienocarb onyl ethylene (FE3), on the reaction kinetics of the dog kidney (Na/K)-ATPase were tested. Besides the conjugated triene moiety of the furylethylene skeleton, the groups responsible for the reaction with nucleophilic groups, the formyl group that connects the second furyl ring in FE1 and FE2 and the formyl group that connects the thienyl ring to the furylethylene moiety in FE3. Among the furylethylenes tested, only FE1 was found to react effectively with beta-mercaptoethanol (beta ME) and glycine (GLY) as model substances containing nucleophilic groups, and also exhibit an inhibitory interaction with the (Na/K)-ATPase. A suppression of the reactivity of the formyl group due to the replacement of the furyl ring with the more aromatic thienyl ring in FE3 did not induce any significant change in the reactivity of the compound with the model substances or with (Na/K)-ATPase. On the other hand, replacement of the NO2 group on the furylethylene moiety (in FE1) by the less electron-attracting phenylsulfonyl group (in FE2 and FE3) yielded a considerable suppression of the inhibitory effect on (Na/K)-ATPase. Moreover, in comparison to FE1, FE2 and FE3 were found to react less potently with the model nucleophilic substances. The results indicated that the conjugated triene moiety on the furylethylene part of the molecule of FE1 may be made responsible for the inhibitory interaction with the nucleophilic aminoacid residue on the (Na/K)-ATPase molecule. FE1 interfered competitively with the (Na/K)-ATPase activation by increasing amounts of potassium. This was manifested by a significant increase in the apparent K0.5App value and a decrease in the apparent cooperativity constant, nApp, for potassium ions, but had no influence on the apparent VmaxApp value for potassium. With respect to the activation of the enzyme with sodium ions and ATP, only FE1 decreased the VmaxApp values while having no considerable influence on the other kinetic variables. It was concluded that FE1 inhibits the (Na/K)-ATPase by selective interaction with some essential nucleophilic (probably SH and/or NH2) aminoacid residues located in, or closed to the potassium binding site of the enzyme molecule.
i）1-（5-硝基-2-呋喃基）-2-苯基磺酰基-2-呋喃甲酰基乙烯（FE1），ii）1-（5-苯基磺酰基-2-呋喃基）-2-苯基磺酰基-2-呋喃甲酰基乙烯（FE2），iii）1-（5-苯基磺酰基-2-呋喃基）-2-苯基磺酰基-2-噻吩甲酰基乙烯（FE3），对犬肾（Na/K）-ATP酶的反应动力学进行了测试。除了呋喃乙烯骨架的共轭三烯部分外，与亲核基团反应的基团，连接FE1和FE2中第二个呋喃环的甲酰基以及连接FE3中噻吩环与呋喃乙烯部分的甲酰基。在所测试的呋喃乙烯中，仅发现FE1能与作为含亲核基团模型物质的β-巯基乙醇（βME）和甘氨酸（GLY）有效反应，并且还与（Na/K）-ATP酶表现出抑制性相互作用。由于在FE3中用更具芳香性的噻吩环取代呋喃环而导致甲酰基反应性的抑制，并未引起该化合物与模型物质或与（Na/K）-ATP酶反应性的任何显著变化。另一方面，用吸电子性较弱的苯基磺酰基（在FE2和FE3中）取代呋喃乙烯部分上的NO2基团（在FE1中），对（Na/K）-ATP酶的抑制作用产生了相当大的抑制。此外，与FE1相比，发现FE2和FE3与模型亲核物质的反应活性较低。结果表明，FE1分子中呋喃乙烯部分的共轭三烯部分可能与（Na/K）-ATP酶分子上的亲核氨基酸残基发生抑制性相互作用有关。FE1通过增加钾的量竞争性地干扰（Na/K）-ATP酶的激活。这表现为表观K0.5App值显著增加，钾离子的表观协同常数nApp降低，但对钾的表观VmaxApp值没有影响。关于用钠离子和ATP激活酶，只有FE1降低了VmaxApp值，而对其他动力学变量没有显著影响。得出的结论是，FE1通过与位于酶分子钾结合位点或其附近的一些必需亲核（可能是SH和/或NH2）氨基酸残基选择性相互作用来抑制（Na/K）-ATP酶。
