Formaldehyde dehydrogenase (FDH) is a member of the zinc-dependent/medium chain alcohol dehydrogenase family. Unlike typical FDH, Pseudomonas putida aldehyde-dismutating FDH (PFDH) is glutathione-independent. PFDH converts 2 molecules of aldehydes to corresponding carboxylic acid and alcohol. MDH family uses NAD(H) as a cofactor in the interconversion of alcohols and aldehydes, or ketones. Like the zinc-dependent alcohol dehydrogenases (ADH) of the medium chain alcohol dehydrogenase/reductase family (MDR), these tetrameric FDHs have a catalytic zinc that resides between the catalytic and NAD(H)binding domains and a structural zinc in a lobe of the catalytic domain. Unlike ADH, where NAD(P)(H) acts as a cofactor, NADH in FDH is a tightly bound redox cofactor (similar to nicotinamide proteins). The medium chain alcohol dehydrogenase family (MDR) has a NAD(P)(H)-binding domain in a Rossmann fold of an beta-alpha form. The N-terminal region typically has an all-beta catalytic domain. These proteins typically form dimers (typically higher plants, mammals) or tetramers (yeast, bacteria), and have 2 tightly bound zinc atoms per subunit.