Aminolyse de carbamates cycliques analogues de la carboxybiotine ; catalyse métallique et modélisation de transfert de carboxyle
摘要:
Aminolysis of carbamic esters, a model of the intermediate carboxybiotin in enzymatic carboxylations was studied in organic medium in the presence of a divalent cation. This study establishes electrostatic catalysis of aminolysis, the rate determining step of which is the collapse of the tetrahedral intermediate principally by carbon-nitrogen bond breacking. The results also account for the role of the divalent cation present in the carboxytransferase subunit of carboxylases.
Effects of Structural Variations on the Rates of Enzymatic and Nonenzymatic Hydrolysis of Carbonate and Carbamate Esters
作者:Munir N. Nassar、Bushra J. Agha、George A. Digenis
DOI:10.1002/jps.2600810321
日期:1992.3
The effect of structuralvariations on the rates of elastase-catalyzed hydrolysis of model carbonate and carbamateesters was studied using HPLC. It is shown that branching in the immediate vicinity of the carbonate or carbamate functionally results in decreased hydrolysisrates. Whereas aryl carbonates act as substrates for elastase, p-nitrophenyl butyl carbamate inhibits the enzyme. A novel method
Hammett analysis of the inhibition of pancreatic cholesterol esterase by substituted phenyl-N-butylcarbamate
作者:Gialih Lin、Cheng-Yue Lai
DOI:10.1016/0040-4039(95)01233-8
日期:1995.8
Substitutedphenyl-N-butylcarbamates (1) as active site-directed irreversible inhibitors of pancreaticcholesterolesterase are investigated for values of the dissociation constant (KI), the carbamylation constant (k2), and the bimolecular rate constant (ki). Linear free energy relationships between-logKI, logk2, or logki and substituent constant (σ) are observed.
Linear free energy relationships of the inhibition of pancreatic cholesterol esterase by 4-Nitrophenyl-N-alkylcarbamate
作者:Gialih Lin、Cheng-Yue Lai
DOI:10.1016/0040-4039(95)02126-4
日期:1996.1
4-Nitrophenyl-N-alkylcarbamates (1) as active site-directed irreversible inhibitors of pancreaticcholesterolesterase are investigated for values of the dissociation constant (Ki), the carbamylation constant (k2), and the bimolecular rate constant (ki). Linear free energy relationships between −logKi, logk2, or logki and polar substituent constant (σ∗) are observed. Taft's Es steric constants are
Structure-Reactivity Relationships as Probes for the Inhibition Mechanism of Cholesterol Esterase by Aryl Carbamates. I. Steady-State Kinetics
作者:Gialih Lin、Cheng-Yue Lai、Wei-Cheng Liao、Bing-Hong Kuo、Chun-Ping Lu
DOI:10.1002/jccs.200000066
日期:2000.6
cies and fol lows the for ma tion of the rel a tively neu tral carbamyl en zymes. For the in hi bi tion of cho les t erol esterase by car ba mates 2 ex cept 4-nitrophenyl-N-phenyl carbamate and 4-nitrophenyl-N-t-butyl carbamate, lin ear re la tion ships of -logKi and logkc with * are ob served and the * val ues are -0.50 and 1.03, re spec tively. Since the above re ac tion also forms the neg a tive-charge
Ortho effects and cross interaction correlations for the mechanisms of cholesterol esterase inhibition by aryl carbamates
作者:Gialih Lin、Yu-Chen Liu、Yon-Gi Wu、Yu-Ru Lee
DOI:10.1002/poc.740
日期:2004.8
Ortho-substituted phenyl-N-butyl carbamates (1–11) were synthesized to evaluate the inhibition mechanisms of porcine pancreatic cholesterol esterase. All carbamateinhibitors act as the active site-directed pseudo substrateinhibitors of the enzymes. The logarithms of dissociation constant (Ki), carbamylationconstant (k2) and bimolecular inhibition constant (ki) multiply linearly correlate with the
邻-取代的苯基- ñ -丁基氨基甲酸酯(1 - 11)的合成以评价猪胰腺的胆固醇酯酶的抑制机制。所有氨基甲酸酯抑制剂均作为酶的活性定点伪底物抑制剂。解离常数的对数(ķ我),氨甲酰常数(ķ 2)和双分子抑制常数(ķ我)乘法线性哈米特取代基常数(σ)相关,塔夫脱Kutter-的Hansch邻位常数(Ë小号),和Swan–Lupton–Hansch的正交极常数(F)。对于–log K i,log k 2和log k i的相关性,普通极性效应(ρ)的反应常数,正向立体常数的强度因子(δ)和正向极化常数的强度因子(f)为0.7 ,-0.07和0.5;0.5、0.04和-0.5;和1.1,-0.03和0.0。–log k i –,log k 2 –和log k i --σ–ασ * –ασσ **相关性的交叉相互作用反应常数(ρXR)分别为 3,-2和1。该ķ我步骤可以由以下两个步骤组成:(1)氨基甲酸酯的质子1