nasA Molybdoenzyme

This basic part encodes the nasA catalytic subunit of nitrite reductase from the ANRA pathway(Lin et al., 1994).

Assimilatory nitrate reduction to ammonium (ANRA) in bacteria occurs through 3 main steps: (1) Nitrate uptake from the extracellular space by a transporter, (2) Conversion of nitrate to nitrite by the nitrate reductase enzyme and (3) Reduction to ammonium of the nitrite by nitrite reductase (Lin & Stewart, 1997).

Usage and Biology

Assimilatory nitrate reductase catalyzes the reduction of nitrate to nitrite once it has been trasported into the intracellular space. It is composed of two subunits: one α-subunit encoded in the nasA and one β-subunit, in addition to one molybdenum-molybdopterin (Mo-MPT) prosthetic group (Coelho & Romão, 2015). nasA encodes for the protein subunit that catalyzes the reduction of nitrate to nitrite.The Mo-MPT cofactor is the active site of the enzyme and is made by one central molybdenum metal atom, chelated by sulphur in the two molybdopterin cofactors and one oxo ligand (Coelho & Romão, 2015). The molybdenum central atom passes between the +4 and the +6 oxidation states, undergoing a reductive elimination to activate itself and an oxidative addition to execute the NO₃^-, reduction. The NO₃^-, substrate is converted into NO₂^-, by the cycle displayed in the figure. Nitrate reductase uses this mechanism to avoid the formation of harmful byproducts, such as nitric oxide (NO), that can affect the organism.

**Reduction reaction of nitrate (NO₃^-, ) to nitrite (NO₂^-, ) by Nitrate Reductase enzyme** (Made in ChemDraw)

Part:BBa_K5306005

Contents

nasA Molybdoenzyme

Usage and Biology

Considerations

Sequence and Features

References