Ab initio QM/MM study shows there is no general acid in the reaction catalyzed by 4-oxalocrotonate tautomerase.

Published

Journal Article

The mechanism for the reaction catalyzed by the 4-oxalocrotonate tautomerase (4-OT) enzyme has been studied using a quantum mechanical/molecular mechanical (QM/MM) method developed in our laboratory. Total free energy barriers were obtained for the two steps involved in this reaction. In the first step, Pro-1 acts as a general base to abstract a proton from the third carbon of the substrate, 2-oxo-4-hexenedioate, creating a negative charge on the oxygen at C-2 of this substrate. In the second step, the same hydrogen abstracted by the N-terminal Pro-1 is shuttled back to the fifth carbon of the substrate to form the product, 2-oxo-3-hexenedioate. The calculated total free energy barriers are 14.54 and 16.45 kcal/mol for the first and second steps, respectively. Our calculations clearly show that there is no general acid in the reaction. Arg-39' ', which is hydrogen bonded to the carboxylate group of the substrate, and an ordered water, which moves closer to the site of the charge formed in the transition state and intermediate, play the main role in transition state/intermediate stabilization without acting as general acids in the reaction.

Full Text

Duke Authors

Cited Authors

  • Cisneros, GA; Liu, H; Zhang, Y; Yang, W

Published Date

  • August 2003

Published In

Volume / Issue

  • 125 / 34

Start / End Page

  • 10384 - 10393

PubMed ID

  • 12926963

Pubmed Central ID

  • 12926963

Electronic International Standard Serial Number (EISSN)

  • 1520-5126

International Standard Serial Number (ISSN)

  • 0002-7863

Digital Object Identifier (DOI)

  • 10.1021/ja029672a

Language

  • eng