Coenzyme F420

Coenzyme F₄₂₀ is a family of coenzymes involved in redox reactions in a number of bacteria and archaea. It is derived from coenzyme F_O (7,8-didemethyl-8-hydroxy-5-deazariboflavin) and differs by having a oligoglutamyl tail attached via a 2-phospho-L-lactate bridge. F₄₂₀ is so named because it is a flavin derivative with an absorption maximum at 420 nm.

F₄₂₀ was originally discovered in methanogenic archaea^[1] and in Actinomycetota (especially in Mycobacterium).^[2] It is now known to be used also by Cyanobacteria and by soil Proteobacteria, Chloroflexi and Firmicutes.^[3] Eukaryotes including the fruit fly Drosophila melanogaster and the algae Ostreococcus tauri also use Coenzyme F_O.^[4]

F₄₂₀ is structurally similar to FMN, but catalytically it is similar to NAD and NADP: it has low redox potential and always transfer a hydride. As a result, it is not only a versatile cofactor in biochemical reactions, but also being eyed for potential as an industrial catalyst. Similar to FMN, it has two states: one reduced state, notated as F₄₂₀-H₂, and one oxidized state, written as just F₄₂₀.^[5] F_O has largely similar redox properties, but cannot carry an electric charge and as a result probably slowly leaks out of the cellular membrane.^[3]

A number of F₄₂₀ molecules, differing by the length of the oligoglutamyl tail, are possible; F₄₂₀-2, for example, refers to the version with two glutamyl units attached. Lengths from 4 to 9 are typical.^[3]