Comparison of enzymatic and non-enzymatic nitroethane anion formation: Thermodynamics and contribution of tunneling

Michael P. Valley, Paul F. Fitzpatrick

Research output: Contribution to journalArticle

30 Scopus citations


In the reaction of nitroalkane oxidase (NAO), the oxidation of nitroalkanes to the corresponding aldehydes or ketones is initiated by the deprotonation of the neutral nitroalkane. The energetics of nitroethane ionization for both the enzymatic and non-enzymatic reactions have been determined by measuring rate constants as a function of temperature. At 25 °C, the rate constant for the acetate-catalyzed reaction is a billionfold smaller than the kcat/Km value for NAO. This corresponds to a difference of 12.3 kcal/mol in the free energy of activation that is largely due to a difference in the activation enthalpy. Analysis of the temperature dependence of the deuterium kinetic isotope effects on the reactions yields similar ΔEa and AH/AD values for the acetate, phosphate, and NAO-catalyzed reactions that fall within the semiclassical limits, consistent with similar contributions of tunneling to the enzymatic and non-enzymatic reactions.

Original languageEnglish (US)
Pages (from-to)6244-6245
Number of pages2
JournalJournal of the American Chemical Society
Issue number20
StatePublished - May 26 2004


ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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