Which gene names correspond to the enzymes converting nitrate to nitrite and nitrite to nitric oxide?

Which gene names correspond to the enzymes converting nitrate to nitrite and nitrite to nitric oxide?

• A. Nitrate reductase genes (Nar) and nitrite reductase genes (Nir)
• B. Nitrite reductase genes (Nir) and nitric oxide synthase genes
• C. NarK and NirK
• D. Nar and Nir (Nitrate reductase and nitrite reductase)

Answer: (B)

The two steps in this part of denitrification are carried out by specific reductases: nitrate reductase converts nitrate to nitrite, and nitrite reductase converts nitrite to nitric oxide. The genes that encode these enzymes are Nar for nitrate reductase and Nir for nitrite reductase. So the pair Nar and Nir directly maps to the enzymes performing those conversions. NarK is a transporter, not a reductase, and nitric oxide synthase is a different enzyme not used in this denitrification step.

The two steps in this part of denitrification are carried out by specific reductases: nitrate reductase converts nitrate to nitrite, and nitrite reductase converts nitrite to nitric oxide. The genes that encode these enzymes are Nar for nitrate reductase and Nir for nitrite reductase. So the pair Nar and Nir directly maps to the enzymes performing those conversions. NarK is a transporter, not a reductase, and nitric oxide synthase is a different enzyme not used in this denitrification step.