LaMotte Nitrate-Nitrogen Enzyme Reduction Test Kit - Manual (Page 3)

non-hazardous nitrate enzyme reductase to reduce nitrate to nitrite,
eliminating heavy metals.
En zyme Tech nol ogy
The Enzyme Vials contain both freeze-dried NADH (nicotinamide adenine
dinucleotide) and YNaR1 (yeast nitrate reductase version 1). The YNaR1 is
a recombinant form of NAD(P)H: Nitrate Reductase (Enzyme Commission
#EC 1.7.1.2). Nitrate Reductase (NaR) is present in all plants and many
types of yeast. It is the enzyme that starts the process of incorporating
nitrogen species into amino acids and proteins in these organisms. The
NaR1 formerly used was extracted from corn leaf. The current YNaR1 is
produced in the Pichia pastoris protein expression system; Pichia is a yeast,
similar to baker’s yeast. YNaR1 is more stable than the native plant enzyme
forms and can be produced cost-effectively by fermentation. A “handle” has
been engineered into the protein to enable purification by affinity
chromatography. Recombinant production eliminates lot-to-lot variation in
protein quality. The YNaR1 enzyme is comprised of two subunits of over 900
amino acids and 3 cofactors each – flavin adenine dinucleotide (FAD or
vitamin B-2), heme iron, and a molybdenum containing group called
molybdopterin.
The reduction of nitrate to nitrite (reduction in oxidation number from +5 to
+3 on the nitrogen by the addition of two electrons) occurs following the
general reaction
NADH + Nitrate à Nitrite + NAD
+
+ OH
_
with YNaR1 acting as the catalyst.
In effect, the electrons are transferred from the NADH to the nitrate
molecule, reducing the nitrate to nitrite.