Solvent Isotope Effects and the Question of Quantum Tunneling in Hydrolytic Enzyme Action

Autor:	Michael P. Garoutte, Jeffrey A. Bibbs, Richard L. Schowen
Rok vydání:	2006
Předmět:	Hydron Nuclear and High Energy Physics Stereochemistry Substrate (chemistry) Catalysis Enzyme catalysis Solvent chemistry.chemical_compound Reaction rate constant Nuclear Energy and Engineering chemistry Kinetic isotope effect Physical chemistry Quantum tunnelling
Zdroj:	Journal of Nuclear Science and Technology. 43:455-460
ISSN:	1881-1248 0022-3131
DOI:	10.1080/18811248.2006.9711123
Popis:	The hydrolysis of acyl-derivatives with catalysis by bovine pancreatic trypsin generates solvent isotope effects on the rate constant k cat (k HOH cat /k DOD cat ) of around 1.5 to 4, depending on the structure of the substrate. The abbreviated substrate N-benzoyl-arginyl ethyl ester has been reported to produce temperature-independent solvent isotope effects of 2.5 to 2.6 between 5 and 45°C, and the measurements are roughly confirmed by new measurements reported here. The previous interpretation, positing formation of a tunneling state followed by quantum tunneling of the hydron, remains possible, but it is now shown that kinetic complexity may in fact be obscuring a traditional temperature dependence of the isotope effect that does not require quantum tunneling.
Databáze:	OpenAIRE
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