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Probing active site geometry using high pressure and secondary isotope effects in an enzyme-catalysed 'deep' H-tunnelling reaction.

ABSTRACT: We report the first study of the effects of hydrostatic pressure on ?-2° KIEs for an enzyme-catalysed H-transfer reaction that occurs by 'deep' tunnelling. High pressure causes a significant decrease in the observed ?-2° KIE on the pre-steady-state hydride transfer from NADH to FMN in the flavoprotein morphinone reductase. We have recently shown that high pressure causes a reduction in macroscopic reaction barrier width for this reaction. Using DFT vibrational analysis of a simple active site model, we posit that the decrease in ?-2° KIE with pressure may arise due to a decrease in the vibrational coupling between the NADH primary (transferred) and secondary hydrogens in the 'tunnelling ready configuration', which more closely resembles the reactant state than the transition state.

SUBMITTER: Hay S

PROVIDER: S-EPMC2948560 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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Probing active site geometry using high pressure and secondary isotope effects in an enzyme-catalysed 'deep' H-tunnelling reaction.

Hay Sam S Pudney Christopher R CR Sutcliffe Michael J MJ Scrutton Nigel S NS

Journal of physical organic chemistry 20100701 7

We report the first study of the effects of hydrostatic pressure on α-2° KIEs for an enzyme-catalysed H-transfer reaction that occurs by 'deep' tunnelling. High pressure causes a significant decrease in the observed α-2° KIE on the pre-steady-state hydride transfer from NADH to FMN in the flavoprotein morphinone reductase. We have recently shown that high pressure causes a reduction in macroscopic reaction barrier width for this reaction. Using DFT vibrational analysis of a simple active site mo ...[more]

PMID: 20890464

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