PDF(Pubmed)
Abstract：
The acyltransferase from Pseudomonas protegens (PpATase) catalyzes in nature the reversible transformation of monoacetylphloroglucinol to diacetylphloroglucinol and phloroglucinol. Interestingly, this enzyme has been shown to catalyze the promiscuous transformation of 3-hydroxyphenyl acetate to 2\',4\'-dihydroxyacetophenone, representing a biological version of the Fries rearrangement. In the present study, we report a mechanistic investigation of this activity of PpATase using quantum chemical calculations. A detailed mechanism is proposed, and the energy profile for the reaction is presented. The calculations show that the acylation of the enzyme is highly exothermic, while the acetyl transfer back to the substrate is only slightly exothermic. The deprotonation of the C6-H of the substrate is rate-limiting, and a remote aspartate residue (Asp137) is proposed to be the general base group in this step. Analysis of the binding energies of various acetyl acceptors shows that PpATase can promote both intramolecular and intermolecular Fries rearrangement towards diverse compounds.
摘要：
来自假单胞菌蛋白原的酰基转移酶(PpATase)在自然界中催化单乙酰间苯三酚向二乙酰间苯三酚和间苯三酚的可逆转化。有趣的是,该酶已被证明可以催化乙酸3-羟基苯酯向2'的混杂转化，4\'-二羟基苯乙酮，代表Fries重排的生物学版本。在本研究中,我们报告了使用量子化学计算对PpATase的这种活性进行的机理研究。提出了一种详细的机制，并给出了反应的能量分布。计算表明，酶的酰化是高度放热的，而转移回底物的乙酰基只是轻微放热。底物C6-H的去质子化是限速的，和远程天冬氨酸残基（Asp137）被建议作为该步骤中的一般碱基基团。对各种乙酰受体的结合能的分析表明，PpATase可以促进分子内和分子间Fries向多种化合物的重排。
