琥珀酸半醛还原酶AKR7A5的稳态动力学机理分析

The steady state kinetic mechanism of succinic semialdehyde reductase AKR7A5

摘要:

琥珀酸半醛还原酶的抑制剂可作为缓解琥珀酸半醛脱氢酶缺陷病症状的潜在药物。研发相应抑制剂需要在理解酶自身动力学性质基础上，阐明抑制剂和酶之间的相互作用机理。目前已解析了两个琥珀酸半醛还原酶的晶体结构，但对酶稳态动力学机理的细节还不够清楚。我们通过对琥珀酸半醛还原酶AKR7A5稳态动力学性质的分析，判断AKR7A5是按照有序的三元复合物反应机理催化反应；在此基础上，推导出琥珀酸半醛发生底物抑制的原因是由于错误地与AKR7A5:NADP+二元复合物结合；底物的结构类似物琥珀酸作为反竞争抑制剂，只能与AKR7A5:NADP+二元复合物结合，这对获得包括琥珀酸在内的反竞争抑制剂与酶的复合物晶体结构，据此对抑制剂进行优化有着重要的指导意义。

Abstract:

The inhibitor of succinic semialdehyde reductase AKR7A5 would be the potential drug for succinic semialdehyde dehydrogenase deficiency. The steady state kinetic mechanism of AKR7A5 and the mechanism of inhibitor interacting with the target enzyme are critical in the development of drug candidates. In spite of two crystal structures of succinic semialdehyde reductases, the details of the kinetic mechanism of AKR7A5 are unclear. Here we report the study of steady state kinetic mechanism of AKR7A5 and found the enzyme reacts in the ordered ternary complex mechanism. Based on the mechanism, we concluded that the substrate inhibition of succinic semialdehyde is caused by the wrong binding to the binary complex AKR7A5 and NADP+. The substrate analogue succinate is uncompetitive inhibitor by binding to the binary complex of AKR7A5 and NADP+. This information is necessary to obtain the ternary complex structure of AKR7A5 and succinate or other uncompetitive inhibitors, as the structural basis for inhibitor optimization.