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Loss of hyperconjugative effects drives hydride transfer during dihydrofolate reductase catalysis

Angelastro, Antonio, Ruiz-Pernía, J. Javier, Tuñón, Iñaki, Moliner, Vicent, Luk, Louis Y. P. and Allemann, Rudolf K. 2019. Loss of hyperconjugative effects drives hydride transfer during dihydrofolate reductase catalysis. ACS Catalysis 9 (11) , pp. 10343-10349. 10.1021/acscatal.9b02839

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Abstract

Hydride transfer is widespread in nature and has an essential role in applied research. However, the mechanisms of how this transformation occurs in living organisms remain a matter of vigorous debate. Here, we examined dihydrofolate reductase (DHFR), an enzyme that catalyzes hydride from C4′ of NADPH to C6 of 7,8-dihydrofolate (H2F). Despite many investigations of the mechanism of this reaction, the contribution of polarization of the π-bond of H2F in driving hydride transfer remains unclear. H2F was stereospecifically labeled with deuterium β to the reacting center, and β-deuterium kinetic isotope effects were measured. Our experimental results combined with analysis derived from QM/MM simulations reveal that hydride transfer is triggered by polarization at the C6 of H2F. The σ Cβ–H bonds contribute to the buildup of the cationic character during the chemical transformation, and hyperconjugation influences the formation of the transition state. Our findings provide key insights into the hydride transfer mechanism of the DHFR-catalyzed reaction, which is a target for antiproliferative drugs and a paradigmatic model in mechanistic enzymology.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Publisher: American Chemical Society
ISSN: 2155-5435
Funders: BBSRC
Date of First Compliant Deposit: 24 October 2019
Date of Acceptance: 23 September 2019
Last Modified: 11 Nov 2019 11:50
URI: http://orca.cf.ac.uk/id/eprint/126290

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