Effect of Pressure on Deuterium Isotope Effects of Yeast Alcohol Dehydrogenase:  Evidence for Mechanical Models of Catalysis†

Biochemistry ◽  
2000 ◽  
Vol 39 (9) ◽  
pp. 2406-2412 ◽  
Author(s):  
Dexter B. Northrop ◽  
Yong-Kweon Cho
Keyword(s):  
Alcohol Dehydrogenase ◽  
Isotope Effects ◽  
Effect Of Pressure ◽  
Yeast Alcohol Dehydrogenase ◽  
Mechanical Models ◽  
Deuterium Isotope Effects

Untersuchungen zur Reaktion der Alkoholdehydrogenase mit Tritium-markierten Substraten

1966 ◽  
Vol 21 (6) ◽  
pp. 540-546 ◽  
Author(s):  
Dieter Palm
Keyword(s):  
Alcohol Dehydrogenase ◽  
Temperature Dependence ◽  
Isotope Effect ◽  
Substrate Binding ◽  
Isotope Effects ◽  
Direct Interaction ◽  
Enzyme Complex ◽  
Temperature Range ◽  
Yeast Alcohol Dehydrogenase ◽  
Rate Controlling Step

Unexpectedly, the isotope effect of ethanol-1-Τ as a substrate of yeast alcohol dehydrogenase, increases with rising temperature from kH/kT = 3.2 at 5 —15°C to 3.8—4.7 at 20 —35 °C. This suggests a change of the rate controlling step as proposed by MÜLLER-HILL and WALLENFELS, who investigated the temperature dependence of the activation energies in this temperature range. A comparison of the affinities of propanol and butanol with the isotope effects of the corresponding tritium labelled compounds (propanol-1-Τ 6.7 at 25 °C, butanol-1-Τ 6.8 at 25 °C) supports the proposal, that during substrate binding, there must be a direct interaction between the enzyme complex and hydrogen which is removed in the reaction. These influences are less pronounced for the ethanol homologues which are bound less tightly to the enzyme. Therefore the H transfering step proper gives a greater contribution to the overall experimental isotope effect.

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