Nitric-oxide reductase

[1][2][3][4] The enzyme participates in nitrogen metabolism and in the microbial defense against nitric oxide toxicity.

Nitric oxide reductase was assigned Enzyme Commission number (EC) 1.7.2.5.

[5]Nitric oxide reductase belongs to the family of oxidoreductases, specifically those acting on other nitrogenous compounds as donors with other acceptors.

The systematic name of this enzyme class is nitrous-oxide:acceptor oxidoreductase (NO-forming).

Other names in common use include nitrogen oxide reductase, and nitrous-oxide:(acceptor) oxidoreductase (NO-forming).

[3] Based on the structure of the enzyme, Shiro 2012 proposes the following mechanism: (1) NO molecules bind at the binuclear center, (2) electrons are transferred from the ferrous irons to the NO, (3) charged NO molecules have the potential to form N to N bonds, and (4) N to O bonds are potentially broken by water, allowing for the N2O and H2O to be released.

[4] According to Hino et al. 2010, the changing charge of the active site causes NO to bind, form N2O and leave the enzyme.

[1] The electro-negative charge reduces the reaction potential for heme b3 and allows NO to bind to the binuclear activation site.

[1] NOR is made up of two subunits, NorC (small) and NorB (large), with a binuclear iron centre.

Figure 1. The Nitrogen Cycle. Nitric oxide (NO) and nitrous oxide (N 2 O) are intermediates in the denitrification of nitrate (NO 3 − ) to nitrogen gas (N 2 ). Nitric oxide reductase reduces NO to N 2 O.