...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Biochemistry >Structural mutations that probe the interactions between the catalytic and dianion activation sites of triosephosphate isomerase
【24h】

Structural mutations that probe the interactions between the catalytic and dianion activation sites of triosephosphate isomerase

机译：探测三磷酸磷酸异构酶催化和二价阴离子活化位点之间相互作用的结构突变

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Triosephosphate isomerase (TIM) catalyzes the isomerization of dihydroxyacetone phosphate to form d-glyceraldehyde 3-phosphate. The effects of two structural mutations in TIM on the kinetic parameters for catalysis of the reaction of the truncated substrate glycolaldehyde (GA) and the activation of this reaction by phosphite dianion are reported. The P168A mutation results in similar 50- and 80-fold decreases in (k_(cat)/K_m)_E and (k_(cat)/K_m)E·HP_i, respectively, for deprotonation of GA catalyzed by free TIM and by the TIM·HPO _3 ~(2-) complex. The mutation has little effect on the observed and intrinsic phosphite dianion binding energy or the magnitude of phosphite dianion activation of TIM for catalysis of deprotonation of GA. A loop 7 replacement mutant (L7RM) of TIM from chicken muscle was prepared by substitution of the archaeal sequence 208-TGAG with 208-YGGS. L7RM exhibits a 25-fold decrease in (k_(cat)/K_m)_E and a larger 170-fold decrease in (k_(cat)/K_m)E·HP_i for reactions of GA. The mutation has little effect on the observed and intrinsic phosphodianion binding energy and only a modest effect on phosphite dianion activation of TIM. The observation that both the P168A and loop 7 replacement mutations affect mainly the kinetic parameters for TIM-catalyzed deprotonation but result in much smaller changes in the parameters for enzyme activation by phosphite dianion provides support for the conclusion that catalysis of proton transfer and dianion activation of TIM take place at separate, weakly interacting, sites in the protein catalyst.
机译：磷酸丙糖异构酶（TIM）催化磷酸二羟丙酮的异构化反应，形成3-磷酸D-甘油醛。报道了TIM中的两个结构突变对催化截短的底物乙醇醛（GA）反应的动力学参数以及亚磷酸二根离子对该反应的活化的影响。 P168A突变导致（k_（cat）/ K_m）_E和（k_（cat）/ K_m）E·HP_i分别减少类似的50倍和80倍，这是由游离TIM和TIM催化的GA去质子化的·HPO _3〜（2-）络合物。该突变对所观察到的和固有的亚磷酸酯二价键结合能或TIM的亚磷酸酯二价键活化以催化GA的去质子作用几乎没有影响。通过用208-YGGS替换古细菌序列208-TGAG来制备来自鸡肌肉的TIM的7环替换突变体（L7RM）。对于GA反应，L7RM的（k_（cat）/ K_m）_E降低25倍，（k_（cat）/ K_m）E·HP_i降低170倍。该突变对观察到的和固有的磷酸二阴离子结合能几乎没有影响，而对TIM的亚磷酸二阴离子活化只有很小的影响。 P168A和loop 7替换突变均主要影响TIM催化的去质子化的动力学参数，但导致亚磷酸根二价阴离子激活酶的参数变化小得多的观察结果为以下结论提供了支持：质子转移催化和二价阴离子活化TIM发生在蛋白质催化剂中单独的，相互作用弱的位置。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号