# 12.1: N and S assimilation from inorganic form


NITROGEN REDUCTION AND ASSIMILATION

Ammonia Synthesis in Plants, fungi, and some microorganisms:

Nitrate Reductase

$\mathrm{NO_{3}^{-}+NADH+H^{+} \Rightarrow NO_{2}^{-}+NAD^{+} + H_{2}O}$

Nitrite Reductase

$\mathrm{NO_{2}^{-}+6Fd_{red}+8H^{+} \Rightarrow NH_{4}^{+}+2H_{2}O+6Fd_{ox}}$

Biological Nitrogen Fixation by microorganisms:

Nitrogenase

$\mathrm{N_{2}+6e^{-}+6H^{+}+~16ATP+16H_{2}O \Rightarrow 2NH_{3}+16ADP+16Pi+16H^{+}}$

Major pathway for ammonia assimilation(=net assimilation in plants, fungi and microorganisms):

Glutamine synthetase (GS)

$\mathrm{NH_{3}+Glu+ATP \Rightarrow Gln+ADP+Pi}$

Glutamate synthase (= GOGAT)

$\mathrm{Gln+\alpha KG+NAD(P)H+H^{+} \Rightarrow 2Glu+ NAD(P)^{+}}$