The Electronic Spectrum of the Prephenate Dianion. An Experimental and Theoretical (MD/QM) Comparison

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• 作者：Adrian E. Roitberg ; Sharon E. Worthington ; Marcia J. Holden ; Martin P. Mayhew ; and Morris Krauss
• 刊名：Journal of the American Chemical Society
• 出版年：2000
• 出版时间：August 2, 2000
• 年：2000
• 卷：122
• 期：30
• 页码：7312 - 7316
• 全文大小：86K
• 年卷期：v.122,no.30(August 2, 2000)
• ISSN：1520-5126

文摘

Prephenate is the product of a Claisen rearrangement of chorismate. The enzyme chorismate mutase(CM from B. subtilis) accelerates the reaction by a factor of 10⁶. The standard method for quantifying prephenatemeasures the electronic absorption spectrum after acid conversion to phenylpyruvate and subsequent alkalinetreatment. To the best of our knowledge, there is no reported UV/Vis spectrum for pure prephenate. Thepresent experimental measurement thus solves this lack of data. A novel molecular dynamics/quantum mechanicsmethod was used to theoretically compute the electronic spectrum, and was used as supporting analysis forthe new experimental spectrum. The agreement between theory and experiment is excellent in the position ofthe absorption peaks, their relative intensities, and their widths. A number of prephenate conformers are possiblein aqueous solution, with the active conformer of CM binding just one conformer which is analogous to thedominant conformer in solution. The conformers are studied in vacuo and in the enzyme active site by abinitio quantum chemical calculations, and in solution with a classical molecular dynamics simulation. Thedata presented here also suggest that the electronic spectrum of prephenate bound to the chorismate mutaseactive site should be observed, even in the presence of other members of the aromatic amino acid pathway.