English
 
Help Privacy Policy Disclaimer
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT

Released

Journal Article

Dynamic Protonation States Underlie Carbene Formation in ThDP-Dependent Enzymes: A Theoretical Study

MPS-Authors
/persons/resource/persons246051

Tittmann,  Kai
Max Planck Institute for Multidisciplinary Sciences, Max Planck Society;

External Resource
No external resources are shared
Fulltext (restricted access)
There are currently no full texts shared for your IP range.
Fulltext (public)

uranga-et-al-2023
(Publisher version), 5MB

Supplementary Material (public)
There is no public supplementary material available
Citation

Uranga, J., Rabe von Pappenheim, F., Tittmann, K., & Mata, R. A. (2023). Dynamic Protonation States Underlie Carbene Formation in ThDP-Dependent Enzymes: A Theoretical Study. The Journal of Physical Chemistry B, 127, 9423-9432. doi:10.1021/acs.jpcb.3c03137.


Cite as: https://hdl.handle.net/21.11116/0000-000E-2735-B
Abstract
The activation mechanism of thiamine diphosphate (ThDP) in enzymes has long been the subject of intense research and controversial discussion. Particularly contentious is the formation of a carbene intermediate, the first one observed in an enzyme. For the formation of the carbene to take place, both intramolecular and intermolecular proton transfer pathways have been proposed. However, the physiologically relevant pH of ThDP-dependent enzymes around neutrality does not seem to be suitable for the formation of such reactive chemical species. Herein, we investigate the general mechanism of activation of the ThDP cofactor in human transketolase (TKT), by means of electronic structure methods. We show that in the case of the human TKT, the carbene species is accessible through a pKa shift induced by the electrostatics of a neighboring histidine residue (H110), whose protonation state change modulates the pKa of ThDP and suppresses the latter by more than 6 pH units. Our findings highlight that ThDP enzymes activate the cofactor beyond simple geometric constraints and the canonical glutamate. Such observations in nature can pave the way for the design of biomimetic carbene catalysts and the engineering of tailored enzymatic carbenes.