Comparative analysis of CO2 reduction by soluble Escherichia coli formate dehydrogenase H and its selenocysteine-to-cysteine substitution variant

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Department of Bioproducts and Biosystems
VTT Technical Research Centre of Finland
Department of Bioproducts and Biosystems
Degree programme
Journal of CO2 Utilization, Volume 77
Metal-dependent formate dehydrogenases (Me-FDHs) are highly active CO2-reducing enzymes operating at low redox potentials and employ either molybdenum or tungsten to reduce the bound substrate. This makes them suitable for electrochemical applications such as fossil-free production of commodity chemicals utilizing renewable energy. Electrocatalytic CO2 reduction by cathode-immobilized Me-FDHs has been recently demonstrated and rational protein engineering can be used to optimize Me-FDHs for various carbon reduction reactions. In the present study, CO2 reduction by soluble monomeric Escherichia coli formate dehydrogenase H (EcFDH-H) was demonstrated and the function of its nucleophilic selenocysteine residue as a transient ligand of a centrally bound molybdenum atom was investigated. Kinetic analysis of the wildtype enzyme revealed maximum CO2 reduction rates of 44 ± 6 s−1 at pH 5.8 that was decreased to 19% and 0% in the case of selenocysteine substitution with the structural homologues cysteine and serine, respectively. Further selenocysteine-to-cysteine substitution effects included an increased acid tolerance as well as stronger inhibition by nitrate and azide indicating a shift of the Mo oxidation state from IV to VI. Conversely, a destabilizing effect on the oxidized Mo(VI) center could be assigned to the native selenocysteine residue that may facilitate the observed efficient CO2 reduction by rapid transition between Mo oxidation states. Taken together, the performed characterization of EcFDH-H as a catalyst for CO2 reduction and the selenocysteine substitution analysis furthers the understanding of the active-site structure of Me-FDHs and thereby supports the development of more efficient biocatalysts for CO2 reduction.
Funding Information: We acknowledge financial support from the Research Council of Finland (formerly known as Academy of Finland) in the form of an Academy Research Fellowship grant awarded to M.L. and funding for the ExtremoForm project granted to S.S. (Decision Nos. 321723 and 329510 , respectively). The authors thank Prof. Shelley D. Minteer for the kind donation of the E. coli strain JG-X. Drs. William E. Robinson of Radboud University and Arnau Bassegoda of the Polytechnic University of Catalonia are thanked for their useful advice for EcFDH-H production. In addition, the assistance provided by Dr. Harry Boer of VTT Technical Research Centre of Finland in revising the manuscript is greatly appreciated. Publisher Copyright: © 2023 The Authors
Carbon dioxide reduction, Formate dehydrogenase, Metalloenzyme, Molybdenum, Selenocysteine
Other note
Li , F , Scheller , S & Lienemann , M 2023 , ' Comparative analysis of CO 2 reduction by soluble Escherichia coli formate dehydrogenase H and its selenocysteine-to-cysteine substitution variant ' , Journal of CO2 Utilization , vol. 77 , 102608 .