O2-tolerant CO dehydrogenase via tunnel redesign for the removal of CO from industrial flue gas

Abstract

Carbon monoxide dehydrogenase (CODH)-catalyzed oxidation of CO to CO 2 provides a promising means of removal of toxic and waste CO from industrial ue gas despite of the lack of active and stable enzymes in the atmosphere. Herein we present rationally and selectively redesigned ChCODH-II (Carboxydothermus hydrogenoformans) variants by engineering gas tunnels in order for O 2 -tolerant CODHs to catalyze e cient CO oxidation under oxygen (O 2 ). Using the redesigned ChCODH-II A559W and A559H variants showing 42-and 128-fold elevation of O 2 tolerance, respectively, complete CO removal was achieved under a near-atmospheric condition. Moreover, these variants e ciently removed CO from industrial ue gas (Linz-Donawiz converter Gas: LDG) discharged from a steel mill despite the high O 2 level (13.4%) during successful and repeated reuse after immobilized on Ni-NTA agarose beads. Our study will provide insights into redesigning the transformation of O 2 -sensitive CODHs into tolerant enzymes for use as workhorses for conversion of toxic or waste gases into safe or value-added chemicals. MainLarge amounts of CO pollutants are emitted from natural sources as well as man-made processes 1 (e.g. annually over 219 billion Nm 3 of CO-containing ue gases from POSCO) 2,3 . Carbon monoxide (CO), the most abundant air pollutant found in the atmosphere other than CO 2 according to the OECD database (https://stats.oecd.org, air emissions source in 2017), can provide su cient carbon and energy sources for converting waste gas to fuels and chemicals through a clean and sustainable method. To convert

Hydrogen-fueled CO2 reduction using oxygen-tolerant oxidoreductases

“…Another possible approach to increase O 2 -tolerance is engineering enzyme. Recently it was reported that the simple point mutations in the gas tunnel region of O 2 -sensitive CO dehydrogenase greatly increased the O 2 -tolerance limit ( Kim et al, 2022 ). We speculate that such enzyme engineering strategy can be applied to ReSH and RcFDH to increase O 2 -tolerance limit.…”

Gas tunnel engineering of prolyl hydroxylase reprograms hypoxia signaling in cells

“…To begin with, we selected W258 and W389 for our studies as tryptophan has been previously shown to function as gates within tunnels to regulate substrate access and enzyme activity. 36,40,41,42 W258 is positioned at the entrance to the tunnel, and W389 is positioned directly in front of the iron center which makes these residues potential entry/exit gates for the O 2 gas. Additionally, both residues are highly conserved among PHD2s ( Fig.…”

Photocatalytic CO2 Reduction Using CO2‐Binding Enzymes

“…Unfortunately, only anaerobic oxygen-sensitive NiÀ FeÀ CODHs are capable of catalyzing CO 2 reduction to CO, [21] which substantially limits the potential applications of these enzymes in waste gas treatment or direct air capture and makes purification of them costly and their practical handling cumbersome. [22] Although significant progress has recently been made in reducing the oxygen sensitivity of CODH-II from Carboxydothermus hydrogenoformans, [23] modifying CODHs remains very limited, as even minor changes in CODH result in a complete loss of activity, [24] hampering further development of these enzymes.…”