酶促反应的“诱导契合-锁钥”模式  

"Induced Fit-Lock and Key" Model in Enzymic Reactions

作　　者：张子剑[1,2] 潘荣[1] 周园[1,2] 赫荣乔[1,2] 

机构地区：[1]中国科学院生物物理研究所,脑与认知国家重点实验室,北京100101 [2]中国科学院研究生院,北京100049

出　　处：《生物化学与生物物理进展》2011年第5期418-426,共9页Progress In Biochemistry and Biophysics

基　　金：国家自然科学基金资助项目(NSFC30870544)~~

摘　　要：在酶学理论中,阐释酶识别底物专一性的代表性学说有"锁钥"和"诱导契合"模型等.作者此前研究了蚯蚓蛋白酶Ⅰ(Eisenia fetida proteaseⅠ,EfP-Ⅰ)的底物专一性,提出了"诱导契合-锁钥"反应模式.然而,采用EfP-Ⅰ建立的模式是否具有普遍的酶学意义需要进一步论证.以蚯蚓蛋白酶Ⅱ(Eisenia fetida proteaseⅡ,EfP-Ⅱ)、枯草杆菌蛋白酶(subtilisin,Sub)以及乳酸脱氢酶(lactate dehydrogenase,LDH)为材料,分别研究了底物反应后酶与其他底物的相互作用.结果显示,经过凝血酶底物chromozym TH(CTH)反应后,蚯蚓蛋白酶Ⅱ和枯草杆菌蛋白酶与尿激酶底物(chromozym U,CU)的反应活性显著降低(P<0.05),表现出符合"诱导契合-锁钥"反应的模式.蚯蚓蛋白酶Ⅱ和枯草杆菌蛋白酶先与CU反应后,却仍能与CTH反应,但后续不能与CU发生反应,仍然表现为"诱导契合-锁钥"模式.另外,丙酮酸反应后的LDH,对乳酸的反应活力显著降低(P<0.05),而乳酸反应后的LDH对丙酮酸的活性却无显著变化.这可能是丙酮酸诱导的LDH构象具有相对的刚性,而乳酸诱导的酶构象具有相对柔性所致.As described in enzymology,＂induced fit＂ and ＂lock and key＂ models are used to explain the enzymic specificity of substrate.Previously,authors have studied the substrate specificity of Eisenia fetida proteaseⅠ（EfP-Ⅰ）,showing that the interaction between this protease and its substrates underwent an ＂induced fit＂ followed by ＂lock and key＂ model.It needs further investigating whether this model is suitable for other enzymes.Here,the reactions of substrate-induced Eisenia fetida proteaseⅡ（EfP-Ⅱ）,subtilisin（Sub） and lactate dehydrogenase（LDH） with their substrates were shown.EfP-Ⅱ and Sub could not recognize chromozym U（CU）（P 〈 0.05） after incubated with chromozym TH（CTH） although the two proteases are natively able to react with both CTH and CU.The reaction followed an ＂induced fit-lock and key＂ pattern.In contrast,the two proteases were still able to react with CTH even though they have been incubated with CU.But neither earthworm protease nor subtilisin could recognize CU after CU and CTH treatment in turn,still suggesting that the reactions followed an ＂induced fit and then lock and key＂ procedure.Furthermore,the activity of LDH with lactate significantly decreased（P 〈 0.05） after the enzyme had been incubated with pyruvate.The activity on the conversion of pyruvate into lactate was not significantly affected by a prior incubation with lactate.This suggests that the pyruvate-induced complementary conformation of LDH is more stable than lactate-induced conformation.

关 键 词：蚯蚓蛋白酶Ⅱ 枯草杆菌蛋白酶 乳酸脱氢酶 锁钥模型 诱导契合模型 诱导契合-锁钥模型 底物专一性 

分 类 号：Q55[生物学—生物化学]