Dwivedi U N, Malhotra O P
Indian J Biochem Biophys. 1989 Dec;26(6):386-9.
Inactivation of isocitrate lyase (native and EDTA-dialysed) by excess tetranitromethane (TNM) exhibits, biphasic kinetics, in which half of the initial activity is lost in a fast and the remaining half in a slow phase each following the pseudo-first order kinetics. Rate constants of the two phases are proportional to the TNM concentration. High succinate concentration protects the enzyme against TNM inactivation only in the slow phase without any effect on the fast phase. With the EDTA-dialysed enzyme, no such protection (against inactivation by TNM) is observed in the presence of succinate or Mg2+ ions. Addition of both these ligands together brings about protection against the slow phase (as with the native enzyme). It has been proposed that the site-site heterogeneity of isocitrate lyase is a consequence of its quaternary structure constraints.
过量四硝基甲烷（TNM）使异柠檬酸裂解酶（天然型和经EDTA透析的）失活呈现双相动力学，其中初始活性的一半在快速阶段丧失，其余一半在缓慢阶段丧失，每个阶段均遵循假一级动力学。两个阶段的速率常数与TNM浓度成正比。高琥珀酸浓度仅在缓慢阶段保护该酶免受TNM失活，对快速阶段无任何影响。对于经EDTA透析的酶，在琥珀酸或Mg2+离子存在下未观察到这种保护作用（防止被TNM失活）。同时添加这两种配体可对缓慢阶段起到保护作用（与天然酶一样）。有人提出，异柠檬酸裂解酶的位点-位点异质性是其四级结构限制的结果。
