The two CO-dehydrogenases of Thermococcus sp. AM4

Abstract

Ni-containing CO-dehydrogenases (CODHs) allow some microorganisms to couple ATP synthesis to CO oxidation, or to use either CO or CO 2 as a source of carbon. The recent detailed characterizations of some of them has evidenced a great diversity in terms of catalytic properties and resistance to O 2. In an effort to increase the number of available CODHs, we have heterologously produced in Desulfovibrio fructosovorans, purified and characterized the two CooS-type CODHs (CooS1 and CooS2) from the hyperthermophilic archaeon Thermococcus sp. AM4 (Tc). We have also crystallized CooS2, which is coupled in vivo to a hydrogenase. CooS1 and CooS2 are homodimers, and harbour five metalloclusters: two NiFe 4 S 4 C clusters, two [4Fe4S] B clusters and one interfacial [4Fe4S] D cluster. We show that both are dependent on a maturase, CooC1 or CooC2, which is interchangeable. The homologous protein CooC3 does not allow Ni insertion in either CooS. The two CODHs from Tc have similar properties: they can both oxidize and produce CO. The Michaelis constants (K m) are in the microM range for CO and in the mM range (CODH 1) or above (CODH 2) for CO 2. Product inhibition is observed only for CO 2 reduction, consistent with CO 2 binding being much weaker than CO binding. The two enzymes are rather O 2 sensitive (similarly to CODH II from Carboxydothermus hydrogenoformans), and react more slowly with O 2 than any other CODH for which these data are available.

Formate Dehydrogenases Reduce CO2 Rather than HCO3−: An Electrochemical Demonstration

“…In all four cases, the final slow decrease in current, in the timescale of minutes, results from the exponential decrease in CO 2 concentration in the cell solution, which slowly equilibrates with the N 2 atmosphere of the glove box. [28,31] The experiments above clearly demonstrate that CO 2 (not bicarbonate) is the substrate of FDH. As a confirmation, we have performed the same series of experiments with CODH adsorbed on the electrode surface, which gave the exact same results (Figure 1 B), consistent with the previous knowledge that CO 2 is the substrate of CODH.…”

“…Both FDH [4] and CODH [28] can be immobilized on electrodes in a configuration in which the enzymes catalyze their respective reactions, producing an electrical current proportional to the turnover frequency. [25,26] We used chronoamperometry, which consists in applying a constant potential to this electrode and monitoring the resulting catalytic current as a function of time.…”

“…AM4 CODH 2. [28] Experimental conditions: T = 25 8C, pH 7 (0.2 M HEPES buffer), electrode rotation rate w = 3000 rpm, E = À0.66 V vs. SHE. The measurements were performed by injecting in the cell at t = 0 s: 5 mM Na 2 CO 3 (blue lines) or 3.7 mM CO 2 (red lines) in the absence (solid lines) and presence (dashed lines) of 5 mg mL À1 carbonic anhydrase.…”

“…The electrode was modified with a film of A) W-dependent Desulfovibrio vulgaris FdhAB[5] (co-adsorbed with polymyxin), and B) Thermococcus sp. AM4 CODH 2 [28]. Experimental conditions: T = 25 8C, pH 7 (0.2 M HEPES buffer), electrode rotation rate w = 3000 rpm, E = À0.66 V vs. SHE.…”

Sensitized Photocatalytic CO2 Reduction With Earth Abundant 3d Metal Complexes Possessing Dipicolyl-Triazacyclononane Derivatives

“…One of the best studied enzymes is carbon dioxide dehydrogenase (CODH) – capable of oxidizing CO to CO 2 and vice versa. The catalytically active C-cluster is composed of a bimetallic Ni-Fe center in a nitrogen/sulfur rich environment ( Lubitz et al, 2014 ; Esselborn et al, 2016 ; Benvenuti et al, 2020 ; Ghosh et al, 2020 ). Beside molecular Ni and Fe complexes, systems containing Co were found to show high electro- as well as photo-catalytic activity towards CO 2 reduction by several groups ( Tamaki and Ishitani, 2017 ; Liu et al, 2018 ).…”