Insights into the O-acetylation reaction of hydroxylated heterocyclic amines by human arylamine N-acetyltransferases: A computational study
Insights into the O-acetylation reaction of hydroxylated heterocyclic amines by human arylamine N-acetyltransferases: A computational study
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DOI：
10.1021/tx0600999
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发表时间：
2006-09-18
影响因子：
4.1
通讯作者：
Lightstone, Felice C.
中科院分区：
文献类型：
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作者：
Lau, Edmond Y.;Felton, James S.;Lightstone, Felice C.
为了更好地理解人类芳胺n -乙酰转移酶（NAT） 1和2之间的差异，进行了一项计算研究。从现有的晶体结构中构建了同源性模型，并比较了这两种酶的活性位点残基125、127和129，从而深入了解了所观察到的底物差异。NAT2模型为理解一些常见多态性如何影响该蛋白的结构提供了基础。对人体NAT模型和模板结构（耻垢分枝杆菌的NAT）进行了分子动力学模拟，结果表明模型是稳定合理的。在NAT1和NAT2模型中对接羟基化杂环胺的研究探讨了这两种蛋白在致突变剂作用下的差异。羟基化的杂环胺只能适应NAT2活性位点，使用我们的模型发现了磷酸盐结合环的替代结合位点，并将进行讨论。对羟基化杂环胺N-OH MeIQx和N-OH PhIP的o -乙酰化反应的量子力学计算表明，这两种化合物的反应座标不同，但分离反应物和产物的激活势垒都很低。本研究结果表明，人类NAT2的常见多态性远离活性位点，更有可能使酶不稳定而不是影响催化作用。此外，量子力学计算表明，N-OH MeIQx和N-OH PhIP的诱变活性差异与它们与NAT的乙酰化反应无关。
A computational study was performed to better understand the differences between human arylamine N-acetyltransferase (NAT) 1 and 2. Homology models were constructed from available crystal structures, and comparisons of the active site residues 125, 127, and 129 for these two enzymes provide insight into observed substrate differences. The NAT2 model provided a basis for understanding how some of the common polymorphisms may affect the structure of this protein. Molecular dynamics simulations of the human NAT models and the template structure (NAT from Mycobacterium smegmatis) were performed and showed the models to be stable and reasonable. Docking studies of hydroxylated heterocyclic amines in the models of NAT1 and NAT2 probed the differences exhibited by these two proteins with mutagenic agents. The hydroxylated heterocyclic amines were only able to fit into the NAT2 active site, and an alternative binding site by the phosphate-binding loop was found using our models and will be discussed. Quantum mechanical calculations on the O-acetylation reaction of the hydroxylated heterocyclic amines N-OH MeIQx and N-OH PhIP show that the reaction coordinates differ for these two compounds, but the activation barrier separating the reactant from the product are both low. The results of this study suggest that common polymorphisms in human NAT2 are distant from the active site and are more likely to destabilize the enzyme than affect catalysis. Additionally, the quantum mechanical calculations show that the observed differences in mutagenic activity between N-OH MeIQx and N-OH PhIP are not related to their acetylation reaction with NAT.