Arylamine N-acetyltransferases （NATs, EC 2.3.1.5） catalyze the N-acetylation of primary arylamines, and play a key role in the biotransformation and metabolism of drugs, carcinogens, etc. In this paper, three possib...Arylamine N-acetyltransferases （NATs, EC 2.3.1.5） catalyze the N-acetylation of primary arylamines, and play a key role in the biotransformation and metabolism of drugs, carcinogens, etc. In this paper, three possible reaction mechanisms are investigated and the results indicate that if the acetyl group directly transfers from the donor to the acceptor, the high activation energies will make it hard to obtain the target products. When using histidine to mediate the acetylation process, these energies will drop in the 15-45 kJ/mol range. If the histidine residue is protonated, the corresponding energies will be decreased by about 35-87 kJ/mol. The calculations predict an enzymatic acetylation mechanism that undergoes a thiolate-imidazolium pair, which agrees with the experimental results very well.展开更多
Both a molecule dynamic study and a combined quantum mechanics and mole-cule mechanics（QM/MM） study on the acetylating deactivation mechanism of isoniazid were presented.This type of reaction was catalyzed by arylam...Both a molecule dynamic study and a combined quantum mechanics and mole-cule mechanics（QM/MM） study on the acetylating deactivation mechanism of isoniazid were presented.This type of reaction was catalyzed by arylamine N-acetyltransferases（NATs） and the results strongly support a direct acetyl group transfer process rather than a stepwise one.The isoniazid was strictly restrained in proper relative position to accept the acetyl group by a Hydrogen-bond network formed by the residues at the active center.The residues,His110 and Cys70,would be functioned as ＇general base＇ rather than ＇general acid＇.If all the residues（including H2O molecules） were removed from the system,the activation energy will be increased from 145.1 to 243.3 kJ/mol.The calculations met the experimental data with good agreement.展开更多
[Objective] This study aimed to analyze the deprotection of acetyl group on amino group. [Method] A simple, convenient one-pot amino protection group of amide removed by thionyl chloride and pyridine via efficient chl...[Objective] This study aimed to analyze the deprotection of acetyl group on amino group. [Method] A simple, convenient one-pot amino protection group of amide removed by thionyl chloride and pyridine via efficient chlorination and hydroly- sis with 1, 2-dichloroethane as solvent at ambient temperature has been developed. [Result] Pyridine is crucial to the reaction; the best solvent is 1, 2-dichloroethane, and the most suitable reaction temperature is the ambient temperature; in addition, the yield is the highest as the molar ratio of pyridine to N-（4-bromophenyl） ac- etamide is 1：1. [Conclusion] The significant features of this protocol include short re- action time, cleaner reaction profiles, under mild reaction conditions and easy purifi- cation, and simple workup that precludes the use of toxic solvents.展开更多
基金the National Natural Scientific Foundation of China(No.20603030)the Youth Natural Science Foundation of Ludong University(No.042902)+1 种基金the Post-doctor Research Foundation of Shandong Province(No.200601007)the Youth Natural Science Foundation of Shandong Provincial Education Department(No.200139)
文摘Arylamine N-acetyltransferases （NATs, EC 2.3.1.5） catalyze the N-acetylation of primary arylamines, and play a key role in the biotransformation and metabolism of drugs, carcinogens, etc. In this paper, three possible reaction mechanisms are investigated and the results indicate that if the acetyl group directly transfers from the donor to the acceptor, the high activation energies will make it hard to obtain the target products. When using histidine to mediate the acetylation process, these energies will drop in the 15-45 kJ/mol range. If the histidine residue is protonated, the corresponding energies will be decreased by about 35-87 kJ/mol. The calculations predict an enzymatic acetylation mechanism that undergoes a thiolate-imidazolium pair, which agrees with the experimental results very well.
基金Supported by the National Natural Science Foundation of China (No. 20603030 and No. 21103080)the Natural Science Foundation of Shandong Province (No. ZR2010BL023)
文摘Both a molecule dynamic study and a combined quantum mechanics and mole-cule mechanics（QM/MM） study on the acetylating deactivation mechanism of isoniazid were presented.This type of reaction was catalyzed by arylamine N-acetyltransferases（NATs） and the results strongly support a direct acetyl group transfer process rather than a stepwise one.The isoniazid was strictly restrained in proper relative position to accept the acetyl group by a Hydrogen-bond network formed by the residues at the active center.The residues,His110 and Cys70,would be functioned as ＇general base＇ rather than ＇general acid＇.If all the residues（including H2O molecules） were removed from the system,the activation energy will be increased from 145.1 to 243.3 kJ/mol.The calculations met the experimental data with good agreement.
文摘[Objective] This study aimed to analyze the deprotection of acetyl group on amino group. [Method] A simple, convenient one-pot amino protection group of amide removed by thionyl chloride and pyridine via efficient chlorination and hydroly- sis with 1, 2-dichloroethane as solvent at ambient temperature has been developed. [Result] Pyridine is crucial to the reaction; the best solvent is 1, 2-dichloroethane, and the most suitable reaction temperature is the ambient temperature; in addition, the yield is the highest as the molar ratio of pyridine to N-（4-bromophenyl） ac- etamide is 1：1. [Conclusion] The significant features of this protocol include short re- action time, cleaner reaction profiles, under mild reaction conditions and easy purifi- cation, and simple workup that precludes the use of toxic solvents.
