物理化学学报 >> 2000, Vol. 16 >> Issue (03): 284-288.doi: 10.3866/PKU.WHXB20000318

研究简报 上一篇    

溶液组成对乌头酸梅构象热稳定性的影响

王邦宁, 韩布兴, 谈夫   

  1. 中国科学院化学研究所,北京 100080
  • 收稿日期:1999-04-09 修回日期:1999-11-15 发布日期:2000-03-15
  • 通讯作者: 王邦宁

Effect of Solution Composition of Thermostability of Aconitase Conformation

Wang Bang-Ning, Han Bu-Xing, Tan Fu   

  1. Institute of Chemistry,Chinese Academy of Sciences,Beijing 100080
  • Received:1999-04-09 Revised:1999-11-15 Published:2000-03-15
  • Contact: Wang Bang-Ning

关键词: 乌头酸梅, 盐键, 热稳定性, 差示扫描量热法

Abstract:

The effect of solution composition on the thermostability of aconitase conformation has been studied by differential scanning calorimetry. In order to know the change of the active site of aconitase ,the three salt links in the active site in the pairs Asp 100•His 101,Asp 165•His 147,and G1u 262•His 167 have been studied by increasing temperature and pH of the solution. At pH 7.47,the calorimetric results demonstrated that the three salt links were broken during heat denaturation and followed by deprotonation of the cationic imidazole groups. Consequently, the number of protons bound to the enzyme molecules in native state is higher than that in denatured state. When pH value was raised to 7.89 or higher, the three salt links could not be formed, consequently Tp/pH was equal to zero. The thermodynamic calculation suggested that the fourth or fifth paired residues as Asp 100•His 101 might exist within the aconitase molecules. The experiments showed that the salts NaCl and NaSCN can raise the thermostability of aconitase, but NaSCN is more effective under the same ionic strength. 0.2 mol•L-1 of NaSCN has the highest ability to raise the thermostability. The chelants SA and OP with antitumor activity can not eliminate the Fe-S cluster within the aconitase molecules and almost not influence its thermostability, but considerably change its denaturational enthalpy. The latter suggests that some relationships may exist between the thermodynamic parameter of enzyme denaturation and antitumor activity of the chelants.

Key words: Aconitase, Salt link, Thermostability, Differential scanning calorimetry