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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.
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. 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 decreased by 35 to 87 kJ / mol. The calculations predict an enzymatic acetylation mechanism that undergoes a thiolate-imidazolium pair, which agrees with the experimental results very well.