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Evidence of negative cooperativity kinetics in F420‐dependent NADP+ oxidoreductase from Archaeoglobus fulgidus

F420H2:NADP+ Oxidoreductase (Fno) catalyzes the reversible reduction of NAPD+ to NADPH, using F420 cofactor as the hydride donor. NADPH production as well as the oxidation of the reduced F420 cofactor are linked to several metabolic pathways including glycolysis and methanogenesis within methanogenic and sulfate‐reducing archaea. Our previous pre steady‐state kinetic studies on Fno have revealed biphasic kinetics with an initial burst phase followed by a subsequent slow phase. The Fno data revealed that the amplitude of the burst phase corresponds to 50% of cofactor reduction. These data suggest this enzyme participates in half site reactivity, while the steady‐state data suggests negative cooperativity. These data suggest that Fno regulates NADPH production methanogenic organisms. Based upon our kinetic studies, we have proposed a chemically plausible mechanism and have identified several key amino acids that potentially play an important role in subunit communication within Fno.