Structural Insights into Microbial One-Carbon Metabolic Enzymes Ni–Fe–S-Dependent Carbon Monoxide Dehydrogenases and Acetyl-CoA Synthases

Abstract

Ni−Fe−S-dependent carbon monoxide dehydrogenases (CODHs) are enzymes that interconvert CO and CO 2 by using their catalytic Ni−Fe−S C-cluster and their Fe−S B-and Dclusters for electron transfer. CODHs are important in the microbiota of animals such as humans, ruminants, and termites because they can facilitate the use of CO and CO 2 as carbon sources and serve to maintain redox homeostasis. The bifunctional carbon monoxide dehydrogenase/acetyl-CoA synthase (CODH/ACS) is responsible for acetate production via the Wood−Ljungdahl pathway, where acetyl-CoA is assembled from two CO 2 -derived one-carbon units. A Ni−Fe− S A-cluster is key to this chemistry. Whereas acetogens use the A-and C-clusters of CODH/ACS to produce acetate from CO 2 , methanogens use A-and C-clusters of an acetyl-CoA decarbonylase/synthase complex (ACDS) to break down acetate en route to CO 2 and methane production. Here we review some of the recent advances in understanding the structure and mechanism of CODHs, CODH/ACSs, and ACDSs, their unusual metallocofactors, and their unique metabolic roles in the human gut and elsewhere.

Evidence for a Putative Isoprene Reductase in Acetobacterium wieringae

“…In the [NiFe]-CODH and ACS, nickel is either next to the Fe/S cluster or substituting an Fe atom in the cluster, while in the [NiFe]-hydrogenase, it located close to the Fe of the Fe(CN) 2 CO group ( 88 ). Based on the protein model, the binding site of cluster V consists of six cysteine residues and has certain conformational resemblances with the Fe/S cluster binding sites in two other enzymes; on one hand, it resembles cluster A of the acetyl-CoA synthase (a Ni-Ni-[4Fe-4S] cluster) ( 89 – 91 ), and, on the other hand, it resembles the site of the P-type cluster in nitrogenases ( 55 ) or the similar double cubane [8Fe-9S] clusters ( 92 ). Interestingly, enzymes containing double cubane clusters have been shown to reduce small molecules such as acetylene to ethylene ( 92 ).…”

Marine Microalgae as a Nutritive Tool to Mitigate Ruminal Greenhouse Gas Production: In Vitro Fermentation Characteristics of Fresh and Ensiled Maize (Zea mays L.) Forage

“…However, the production obtained with the addition of the microalgae was suggested to be caused by acetogenesis, since the inhibition of methanogenesis favors the increase of reducing acetogens [ 58 ], which increases the reduction of CO 2 to CO. In addition, some carbon monoxide dehydrogenase enzymes involved in the Wood–Ljungdahl pathway during CO 2 reduction are dependent on mineral availability [ 66 ], so the effect of the mineral profile of the microalgae cannot be disregarded ( Table 2 ).…”

[Fe]‐Hydrogenase, Cofactor Biosynthesis and Engineering

“…Formate is oxidized to reduce ferredoxin or to transfer low‐potential electrons to Fmd [11a] . The only known enzyme that reacts with CO in M. maripaludis is the nickel‐containing CO dehydrogenase, which catalyzes the reversible reduction of CO 2 to CO using ferredoxin as an electron carrier [48] . Based on this information, we can think about a common electron carrier capable of being reduced in the metabolism from H 2 , formate and/or CO.…”

“…[11a] The only known enzyme that reacts with CO in M. maripaludis is the nickel-containing CO dehydrogenase, which catalyzes the reversible reduction of CO 2 to CO using ferredoxin as an electron carrier. [48] Based on this information, we can think about a common electron carrier capable of being reduced in the metabolism from H 2 , formate and/or CO. This hypothesized electron carrier is ferredoxin or its analogs (e. g. flavodoxin).…”