Chemoselectivity in cytochrome c catalyzed carbene transfer into Si-H and N-H bonds

In a new study published in the Journal of the American Chemical Society, Dr. Marc Garcia-Borr s reports a joint computational and experimental study together with the groups of Prof. Frances Arnold (Caltech, USA) and Prof. Ken Houk (UCLA, USA) to characterize the mechanism and chemoselective formation of carbon-silicon bonds. This process occurs via carbene insertions into Si-H bonds and is catalyzed by a previously evolved cytochrome c carbene transferase from Rhodothermus marinus (Rma cyt c, Science, 2016, 354, 1048-1051).

Using multiscale computational approaches combined with experimental characterizations, it was determined how this enzyme-catalyzed reaction works. The authors discovered that mutations introduced by directed evolution impact mainly the control of conformational dynamics of a protein loop that covers the substrate access to the iron-carbene active species. Using extensive molecular dynamics (MD) simulations it was found that by modifying the loop conformational dynamics, the enzymatic activity could be enhanced up to 7-fold. More importantly, this loop is responsible for the chemoselectivity control acquired by the enzyme during evolution, by controlling how the substrate approaches the iron-carbene intermediate.

Taking advantage of the new mechanistic insights, the loop conformational dynamics was further manipulated to switch the enzyme chemoselectivity from silylation to amination (from >97% silylation in the Rma TDE variant to >90% amination in a new Rma TDFPI variant) using a substrate containing both NáH and SiáH functionalities.

This study demonstrates that information on protein structure and conformational dynamics, combined with knowledge of mechanism, leads to understanding of how non-natural and selective chemical transformations can be introduced into the biological world, and provides better understanding of how abiological carbene transferases control chemoselectivity.

The Research Team headed by Dr. Garcia-Borr s is currently applying these computational approaches to investigate and characterize the formation of key enzymatic intermediates, with the final aim to design new enzymes that catalyze new-to-nature reactions interesting from a synthetic perspective.

The paper has recently been published in the Journal of the American Chemical Society:

M. Garcia-Borr s, S.B.J. Kan, R.D. Lewis, A. Tang, G. Jimenez-Osá®s, F.H. Arnold, and K.N. Houk
“Origin and Control of Chemoselectivity in Cytochromec Catalyzed Carbene Transfer into Si-H and N-H bonds”
J. Am. Chem. Soc. 2021, online, ASAP
DOI: 10.1021/jacs.1c02146

Girona, May 4, 2021
More information: gestor.iqcc@gmail.com