Current status of carbon monoxide dehydrogenases (CODH) and their potential for electrochemical applications

Anthropogenic carbon dioxide (CO₂) levels are rising to alarming concentrations in earth's atmosphere, causing adverse effects and global climate changes. In the last century, innovative research on CO₂ reduction using chemical, photochemical, electrochemical and enzymatic approaches has been addressed. In particular, natural CO₂ conversion serves as a model for many processes and extensive studies on microbes and enzymes regarding redox reactions involving CO₂ have already been conducted. In this review we focus on the enzymatic conversion of CO₂ to carbon monoxide (CO) as the chemical conversion downstream of CO production render CO particularly attractive as a key intermediate. We briefly discuss the different currently known natural autotrophic CO₂ fixation pathways, focusing on the reversible reaction of CO₂, two electrons and protons to CO and water, catalyzed by carbon monoxide dehydrogenases (CODHs). We then move on to classify the different type of CODHs, involved catalyzed chemical reactions and coupled metabolisms. Finally, we discuss applications of CODH enzymes in photochemical and electrochemical cells to harness CO₂ from the environment transforming it into commodity chemicals.