Reactivity of horse liver alcohol dehydrogenase with 3-methylcyclohexanols

The specificity of horse liver alcohol dehydrogenase for cyclohexanol and its 3-methyl derivatives was investigated by stopped-flow and initial velocity kinetic studies. The (1S,3S)-3-methylcyclohexanol was 7 times more reactive (V/Km) than cyclohexanol, whereas the (1R,3R)-3-methylcyclohexanol was at least 1000 times less reactive than its enantiomer. Computer simulation of the transient reaction of NAD+ and the cyclohexanols catalyzed by the enzyme suggests that the rate of transfer of hydrogen from the alcohol to NAD+ is increased with the 1S,3S isomer. Modeling of the three-dimensional structure of the ternary complex of the enzyme suggests that the 1S,3S isomer should only bind in a productive, reactive mode, whereas the 1R,3R isomer would bind predominantly in a nonproductive, inhibitory mode.