Enzyme dynamics and hydrogen tunnelling in a thermophilic alcohol dehydrogenase

• Published in: Nature (London) Vol. 399; no. 6735; pp. 496 - 499
• Main Authors: Klinman, Judith P, Kohen, Amnon, Cannio, Raffaele, Bartolucci, Simonetta
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 03-06-1999; Nature Publishing Group
• Subjects: Alcohol Dehydrogenase - chemistry; Alcohol Dehydrogenase - metabolism; Analytical, structural and metabolic biochemistry; Bacillus stearothermophilus; Benzyl Alcohol - metabolism; Biological and medical sciences; Catalysis; Chemical bonds; Chemical reactions; Dehydrogenase; Enzymes; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Geobacillus stearothermophilus - enzymology; High temperature; Hydrogen; Hydrogen - chemistry; Models, Chemical; Molecular biology; NAD - metabolism; Oxidoreductases; Temperature; Enzymatic activity; Enzyme; Reaction mechanism; Thermophily; Oxidoreductases; Alcohol dehydrogenase; Kinetics
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/20981

Biological catalysts (enzymes) speed up reactions by many orders of magnitude
using fundamental physical processes to increase chemical reactivity. Hydrogen
tunnelling has increasingly been found to contribute to enzyme reactions at
room temperature. Tunnelling is the phenomenon by which a particle
transfers through a reaction barrier as a result of its wave-like property. In reactions involving small molecules, the relative importance
of tunnelling increases as the temperature is reduced. We have
now investigated whether hydrogen tunnelling occurs at elevated temperatures
in a biological system that functions physiologically under such conditions.
Using a thermophilic alcohol dehydrogenase (ADH), we find that hydrogen tunnelling
makes a significant contribution at 65 °C; this is analogous to
previous findings with mesophilic ADH at 25 °C (
ref. 5). Contrary to predictions for tunnelling through a rigid
barrier, the tunnelling with the thermophilic ADH decreases at and below room
temperature. These findings provide experimental evidence for a role of thermally
excited enzyme fluctuations in modulating enzyme-catalysed bond cleavage.