Abstract
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 language | English (US) |
|---|---|
| Pages (from-to) | 6244-6245 |
| Number of pages | 2 |
| Journal | Journal of the American Chemical Society |
| Volume | 126 |
| Issue number | 20 |
| DOIs | |
| State | Published - May 26 2004 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Chemistry(all)
Cite this
Comparison of enzymatic and non-enzymatic nitroethane anion formation : Thermodynamics and contribution of tunneling. / Valley, Michael P.; Fitzpatrick, Paul F.
In: Journal of the American Chemical Society, Vol. 126, No. 20, 26.05.2004, p. 6244-6245.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Comparison of enzymatic and non-enzymatic nitroethane anion formation
T2 - Thermodynamics and contribution of tunneling
AU - Valley, Michael P.
AU - Fitzpatrick, Paul F
PY - 2004/5/26
Y1 - 2004/5/26
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=2442661476&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=2442661476&partnerID=8YFLogxK
U2 - 10.1021/ja0484606
DO - 10.1021/ja0484606
M3 - Article
C2 - 15149217
AN - SCOPUS:2442661476
VL - 126
SP - 6244
EP - 6245
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 20
ER -