Formate dehydrogenase

Formate dehydrogenases are a set of enzymes that catalyse the oxidation of formate to carbon dioxide, donating the electrons to a second substrate, such as NAD+ in formate:NAD+ oxidoreductase (EC 1.2.1.2) or to a cytochrome in formate:ferricytochrome-b1 oxidoreductase (EC 1.2.2.1).

Biological function
NAD-dependent formate dehydrogenases are important in methylotrophic yeast and bacteria and are vital in the catabolism of C1 compounds such as methanol. The cytochrome-dependent enzymes are more important in anaerobic metabolism in prokaryotes. For example, in E. coli, the formate:ferricytochrome-b1 oxidoreductase is an intrinsic membrane protein with two subunits and is involved in anaerobic nitrate respiration.

NAD-dependent reaction

Formate + NAD+ ↔ CO2 + NADH + H+

Cytochrome-dependent reaction

Formate + 2 ferricytochrome b1 ↔ CO2 + 2 ferrocytochrome b1 + 2 H+

Molybdopterin, molybdenum and selenium dependence
One of the enzymes in the oxidoreductase family that sometimes employ tungsten (bacterial formate dehydrogenase H) is known to use a selenium-molybdenum version of molybdopterin.

Transmembrane domain
The transmembrane domain of the beta subunit of formate dehydrogenase consists of a single transmembrane helix. This domain acts as a transmembrane anchor, allowing the conduction of electrons within the protein.