经常建议酶催化的磷酰基转移反应通过从其溶液对应物改变的过渡态进行。然而,先前对大肠杆菌碱性磷酸酶 (AP) 的研究表明,这种酶通过松散的解离过渡态催化磷酸单酯的水解,类似于溶液中的过渡态。尽管在溶液中磷酸二酯水解具有更紧密、更缔合的过渡态,但 AP 还表现出催化混杂,具有低水平的磷酸二酯酶活性。因为 AP 在进化上针对磷酸单酯水解进行了优化,所以活性位点环境可能会改变二酯水解的过渡状态,使其与传入和传出基团的键合更松散。为了测试这种可能性,我们已经测量了一系列取代的甲基苯基磷酸二酯的非酶促和 AP 催化的反应速率。beta(lg) 的值和其他数据表明 AP 催化的磷酸二酯水解的过渡态与溶液中的过渡态无法区分。AP 通过识别和稳定类似于水溶液中的过渡态来催化磷酰基转移反应,而不是改变过渡态结构。因此,AP 活性位点能够识别不同的过渡状态,这一特性有助于混杂活动的进化优化。beta(lg) 的值和其他数据表明
Structure-reactivity correlations for reactions of substituted phenolate anions with acetate and formate esters
作者:Dimitrios Stefanidis、Sayeon Cho、Sirano Dhe-Paganon、William P. Jencks
DOI:10.1021/ja00058a006
日期:1993.3
substituted phenolate anions with m-nitrophenyl, p-nitrophenyl, and 3,4-dinitrophenyl formates follow nonlinear BrOnsted-type correlations that might be taken as evidence for a change in the rate-limiting step of a reaction that proceeds through a tetrahedral addition intermediate. However, the correlation actually represents two different BrOnsted lines that are defined by meta- and para-substituted phenolate
71) fitting the 0.5−0.7 range commonly found for SNAr reactions, those for the various oximates studied do not define a meaningful linear plot. Interestingly, the observed variations in k1Ox reveal a tendency of the reactivity of oximates of pKa > 7.5−8 to level off rapidly, a situation reminiscent of that encountered in other nucleophilic reactions of these species at carbonyl and phosphonyl centres
Concerted acetyl-group transfer between substituted phenolate ion nucleophiles: variation of transition-state structure as a function of substituent
作者:Salem Ba-Saif、Ajay K. Luthra、Andrew Williams
DOI:10.1021/ja00189a045
日期:1989.3
The α-Effect in Methyl Transfers from <i>S</i>-Methyldibenzothiophenium Fluoroborate to Substituted <i>N</i>-Methylbenzohydroxamates
作者:K. R. Fountain、Cassie J. Felkerson、Jeremy D. Driskell、Brian D. Lamp
DOI:10.1021/jo0206263
日期:2003.3.1
tightness. The alpha-effects for the series of sulfonium salts in completion reactions for 3-ClNMBH anions and 3-nitrophenolate anions are (log k(alpha)/k(normal)) 1.124 for dimethylphenyl sulfonium, 1.512 for dimethyl-1-naphthyl sulfonium, 1.835 for dimethyl-9-anthracenyl sulfonium, and 1.137 for S-methyldibenzylthiophenium. Correlations of the sizes of alpha-effects with typical SET (or ET) experimental parameters
Alkaline Phosphatase Mono- and Diesterase Reactions: Comparative Transition State Analysis
作者:Jesse G. Zalatan、Daniel Herschlag
DOI:10.1021/ja056528r
日期:2006.2.1
Escherichia coli alkaline phosphatase (AP), however, suggests that this enzyme catalyzes the hydrolysis of phosphatemonoesters through a loose, dissociative transition state, similar to that in solution. AP also exhibits catalytic promiscuity, with a low level of phosphodiesterase activity, despite the tighter, more associative transition state for phosphatediesterhydrolysis in solution. Because AP
经常建议酶催化的磷酰基转移反应通过从其溶液对应物改变的过渡态进行。然而,先前对大肠杆菌碱性磷酸酶 (AP) 的研究表明,这种酶通过松散的解离过渡态催化磷酸单酯的水解,类似于溶液中的过渡态。尽管在溶液中磷酸二酯水解具有更紧密、更缔合的过渡态,但 AP 还表现出催化混杂,具有低水平的磷酸二酯酶活性。因为 AP 在进化上针对磷酸单酯水解进行了优化,所以活性位点环境可能会改变二酯水解的过渡状态,使其与传入和传出基团的键合更松散。为了测试这种可能性,我们已经测量了一系列取代的甲基苯基磷酸二酯的非酶促和 AP 催化的反应速率。beta(lg) 的值和其他数据表明 AP 催化的磷酸二酯水解的过渡态与溶液中的过渡态无法区分。AP 通过识别和稳定类似于水溶液中的过渡态来催化磷酰基转移反应,而不是改变过渡态结构。因此,AP 活性位点能够识别不同的过渡状态,这一特性有助于混杂活动的进化优化。beta(lg) 的值和其他数据表明