CODH-IV: A High-Efficiency CO-Scavenging CO Dehydrogenase with Resistance to O2

CO dehydrogenases (CODHs) catalyse the reversible conversion between CO and CO2. Genomic analysis indicated that the metabolic functions of CODHs vary. The genome of Carboxydothermus hydrogenoformans encodes five CODHs (CODH-I-V), of which CODH-IV is found in a gene cluster near a peroxide-reducing enzyme. Our kinetic and crystallographic experiments reveal that CODH-IV differs from other CODHs in several characteristic properties: it has a very high affinity for CO, oxidizes CO at diffusion-limited rate over a wide range of temperatures, and is more tolerant to oxygen than CODH-II. Thus, our observations support the idea that CODH-IV is a CO scavenger in defence against oxidative stress and highlight that CODHs are more diverse in terms of reactivity than expected.