酶催化反应平衡常数的一级和二级氘同位素效应。

Primary and secondary deuterium isotope effects on equilibrium constants for enzyme-catalyzed reactions.

作者信息

Cook P F, Blanchard J S, Cleland W W

出版信息

Biochemistry. 1980 Oct 14;19(21):4853-8. doi: 10.1021/bi00562a023.

Abstract

Primary deuterium equilibrium isotope effects for the reaction of five secondary alcohols with nicotinamide adenine dinucleotide (DPN) to give reduced deuterionicotinamide adenine dinucleotide (DPND) (cyclohexanol-1-d, 1.18; 2-propanol-2-d, 1.175; threo-DL-isocitrate-2-d, 1.168; L-malate-2-d, 1.173; L-lactate-2-d, 1.19) are all approximately 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-1-d, it is 1.28. In each case deuterium becomes enriched in the alcohol, amino acid, or hemiacetal with respect to DPNH (TPNH). beta-Secondary equilibrium isotope effects for reduction of ketones by DPNH (cyclohexanone-2,2,6,6-d4, 0.82; acetone-d6, 0.78; pyruvate-d3, 0.83; alpha-ketoglutarate-3,3-d2 reduced to glutamate, 0.898; oxaloacetate-3,3-d2, 0.877; oxaloacetate-3R-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-1-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-1-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-d2 to malate, the value is 0.69, with deuterium becoming enriched in L-malate. The equilibrium isotope effect for reaction of cyclohexanol-1-d with DPN is temperature independent over the range 15-35 degrees C.

摘要

五种仲醇与烟酰胺腺嘌呤二核苷酸（DPN）反应生成还原型氘代烟酰胺腺嘌呤二核苷酸（DPND）的一级氘平衡同位素效应（环己醇 -1 -d，1.18；2 -丙醇 -2 -d，1.175；苏式 -DL -异柠檬酸 -2 -d，1.168；L -苹果酸 -2 -d，1.173；L -乳酸 -2 -d，1.19）均约为 1.18，而对于伯醇乙醇，该值为 1.07，对于氨基酸 L -谷氨酸 -2 -d，为 1.14，对于半缩醛葡萄糖 -1 -d，为 1.28。在每种情况下，相对于 DPNH（TPNH），氘在醇、氨基酸或半缩醛中富集。DPNH 还原酮的β -仲平衡同位素效应（环己酮 -2,2,6,6 -d4，0.82；丙酮 -d6，0.78；丙酮酸 -d3，0.83；α -酮戊二酸 -3,3 -d2 还原为谷氨酸，0.898；草酰乙酸 -3,3 -d2，0.877；草酰乙酸 -3R -d，0.945）的平均值为 0.946/D，相对于酮，氘在醇或氨基酸中富集。对于 DPNH 还原乙醛 -1 -d，观察到的值 0.953 除了包括对还原的影响外，还包括对水合平衡的平衡效应，游离醛和水合物还原的计算值分别为 0.78 和 1.07。对于未水合的苯甲醛 -1 -d 的还原，观察到的值为 0.79。DPN -4 -d 转化为 DPNH 的二级平衡同位素效应为 0.89，氘在 DPNH 中富集，富马酸 -2,3 -d2 转化为苹果酸的二级平衡同位素效应为 0.69，氘在 L -苹果酸中富集。环己醇 -1 -d 与 DPN 反应的平衡同位素效应在 15 - 35℃范围内与温度无关。