TY - JOUR
T1 - Primary And Secondary Deuterium Isotope Effects On Equilibrium Constants For Enzyme-Catalyzed Reactions
AU - Cook, Paul F.
AU - Blanchard, John S.
AU - Cleland, W. W.
PY - 1980/2/1
Y1 - 1980/2/1
N2 - Primary deuterium equilibrium isotope effects for the reaction of five secondary alcohols with nicotinamide adenine dinucleotide (DPN) to give reduced deutcrionicotinamide adenine dinucleotide (DPND) (cyclohexanol-l-d, 1.18; 2-propanol-2-d, 1.175; threo-DL-isocitrate-2-d, 1.168; L-ma-late-2-d, 1.173; L-lactate-2-d. 1.19) are all ~ 1.18. while for a primary alcohol, ethanol, the value is 1.07, for an amino acid, L-glutamate-2-d, it is 1.14, and for a hemiacetal, glucose-l-d, it is 1.28. In each case deuterium becomes enriched in the alcohol, amino acid, or hemiacetal with respect to DPNH (TPNH). β-Secondary equilibrium isotope effects for reduction of ketones by DPNH (cyclohexanone-2, 2, 5,> 5-4, 0.81; acetone-d6, 0.78; pyruvate-d3, 0.83; β-ketoglutarate-5, 3-d2reduced to glutamate, 0.898; oxaloacetate-3, 3-d2, 0.877; oxaIoacetate-3, 3-d, 0.945) give an average value of 0.946/D, with deuterium becoming enriched in the alcohol or amino acid with respect to the ketone. For reduction of acetaldehyde-l-d by DPNH, the observed value of 0.953 includes the equilibrium effect on the hydration equilibrium in addition to that on the reduction, and the calculated values for reduction of the free aldehyde and the hydrate are 0.78 and 1.07. For reduction of benzaldehyde-l-d, which is not hydrated, the observed value was 0.79. The secondary equilibrium isotope effect for conversion of DPN-4-d to DPNH is 0.89, with deuterium becoming enriched in DPNH, and, for conversion of fumarate-2, 3-d2to malate, the value is 0.69, with deuterium becoming enriched in L-malate. The equilibrium isotope effect for reaction of cyclohexanol-Z-rf with DPN is temperature independent over the range 15-35 °C.
AB - Primary deuterium equilibrium isotope effects for the reaction of five secondary alcohols with nicotinamide adenine dinucleotide (DPN) to give reduced deutcrionicotinamide adenine dinucleotide (DPND) (cyclohexanol-l-d, 1.18; 2-propanol-2-d, 1.175; threo-DL-isocitrate-2-d, 1.168; L-ma-late-2-d, 1.173; L-lactate-2-d. 1.19) are all ~ 1.18. while for a primary alcohol, ethanol, the value is 1.07, for an amino acid, L-glutamate-2-d, it is 1.14, and for a hemiacetal, glucose-l-d, it is 1.28. In each case deuterium becomes enriched in the alcohol, amino acid, or hemiacetal with respect to DPNH (TPNH). β-Secondary equilibrium isotope effects for reduction of ketones by DPNH (cyclohexanone-2, 2, 5,> 5-4, 0.81; acetone-d6, 0.78; pyruvate-d3, 0.83; β-ketoglutarate-5, 3-d2reduced to glutamate, 0.898; oxaloacetate-3, 3-d2, 0.877; oxaIoacetate-3, 3-d, 0.945) give an average value of 0.946/D, with deuterium becoming enriched in the alcohol or amino acid with respect to the ketone. For reduction of acetaldehyde-l-d by DPNH, the observed value of 0.953 includes the equilibrium effect on the hydration equilibrium in addition to that on the reduction, and the calculated values for reduction of the free aldehyde and the hydrate are 0.78 and 1.07. For reduction of benzaldehyde-l-d, which is not hydrated, the observed value was 0.79. The secondary equilibrium isotope effect for conversion of DPN-4-d to DPNH is 0.89, with deuterium becoming enriched in DPNH, and, for conversion of fumarate-2, 3-d2to malate, the value is 0.69, with deuterium becoming enriched in L-malate. The equilibrium isotope effect for reaction of cyclohexanol-Z-rf with DPN is temperature independent over the range 15-35 °C.
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U2 - 10.1021/bi00562a023
DO - 10.1021/bi00562a023
M3 - Article
C2 - 7000186
AN - SCOPUS:0019194597
SN - 0006-2960
VL - 19
SP - 4853
EP - 4858
JO - Biochemistry
JF - Biochemistry
IS - 21
ER -