Nitric Oxide Dioxygenase - Reaction Mechanism

Reaction Mechanism

The mechanism of action has still not been entirely deduced, however, the leading theory suggests that the conversion is carried out through a series of redox reactions involving iron centers as shown in the series of half reactions below:

Step Reaction
FAD reduction NAD(P)H + FAD + H+ → NAD(P)+ + FADH2
Iron reduction 1 FADH2 + Fe3+ → Fe2+ + FADH + H+
Iron Reduction 2 FADH + Fe3+ → FAD + Fe2+ + H+
O2 Binding Fe2+ + O2 → Fe3+(O2-)
NO dioxygenation Fe3+(O2-) + NO → Fe3+ + NO3-

Another theory developed more recently (2009) suggests that a NO dioxygenase activity could also proceed through phenolic nitration via a putative heme-peroxynitrite intermediate.

The most well studied NO dioxygenase is flavohemoglobin (flavoHb), shown to the right: Studies have shown that flavohemoglobins are induced by NO, nitrite, nitrate, and NO-releasing agents in various bacteria and fungi. Additionally, flavoHbs have been shown to protect bacteria, yeast, and Dictyostelium discoideum against growth inhibition and damage mediated via NO.

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