Agriculture Reference
In-Depth Information
FIGURE 2:
Main reactions involved in nitrogen assimilation in higher plants. NO
3
−
= nitrate; NO
2
−
= nitrite; NH
4
+
= ammonium, N
2
=
atmospheric dinitogen. The main enzymes involved in nitrate reduction and ammonia assimilation are indicated in italics: NR = nitrate
reductase; NiR = nitrite reductase; Nase = nitrogenase; GS = glutamine synthetase; GOGAT = glutamate synthase. The ultimate source
of inorganic N available to the plant is ammonium, which is incorporated into organic molecules in the form of Glutamine and Glutamate
through the combined action of the two enzymes GS and GOGAT. Carbon originating from photosynthesis through the tricarboxylic acid
cycle (TCA cycle) provides the α-ketoglutarate needed for the reaction catalyzed by the enzyme GOGAT. Amino acids are further used for
the synthesis of proteins, nucleotides and all N-containing molecules.
