Kinetic isotope effects 1,4-dihydropyridine

Examination of one real-life case may benefit the reader s understanding. Strittmatter studied the primary kinetic isotope effects arising in the NADH-dependent cytochrome bs reductase (EC 1.6.2.2). The oxidation of NADH and subsequent reduction of cytochrome bs is facilitated by the enzyme-bound FAD group, and the kinetics of the direct transfer of a hydrogen from the A-face (or pro-R) of NADH to the flavin can be monitored by the loss of the 340 run absorbance of the NADH s dihydropyridine ring. Using deuterated isotopic isomers of NADH and several related compounds, Strittmatter obtained the primary kinetic isotope effect data compiled in the table below. 

Based on the fact that the hyd -dihydropyridine ring transfers d hydride transfer mechanism propos in early days has been accepted consider the polarization where on a less electronegative hydr connection it was suggested that an initial one-electron transfer corresponds to an ion radical between the substrate and the 1, electron transfer mechanism (ET Steffens and Chipman (1971) bas kinetic isotope effect associated... 

Kinetic and product isotope effect discrepancies 95 Oxidations by inorganic oxidants and quinones 95 Substituent effects on rates and equilibria 98 Miscellaneous reactions of dihydropyridines 101 Secondary hydrogen isotope effects 102 Theoretical studies 103 References 105... 

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