Question

Trace the path of nitrogen from atmospheric N2 into glutamate. Name the enzymes, substrates, products, and coenzymes.

Answer 1

Firstly the nitrogen molecule,
`$N_2 $` is reduced to to
`$NH_3$` (ammonia) in the reaction that is catalyzed by nitrogenase complex. It is present in the certain prokaryotes, which includes some of the live symbiotically with the legumes

`$N_2 + 10H^ + + 8e^- + 14 \ ATP \rightarrow 2NH_4^+ + 16ADP + 16Pi + H_2$`

The ammonia is then incorporated into the glutamine in reaction that is catalyzed by the glutamine synthetase:

`$\text{glutamate} + NH_4^+ + ATP \rightarrow \text{ glutamine} \ + ADP + Pi + H^+$`

And finally the glutamate synthase that catalyzes the formation of the glutamate from the glutamine :

α-Ketoglutarate + glutamine + NADPH +
`$H^+ \rightarrow 2 \ glutamate + NADP^+ $`

Also there is an alternative minor route for the formation of glutamate from ammonia that involves reaction catalyzed bu the glutamate dehydrogenase :

`$\alpha - \text{Ketoglutarate} + NH_4^+ + NADPH \rightarrow \text{ glutamate} \ NADP^+ + H_2O $`

Answer 2

The path of the atmospheric nitrogen to the glutamate involves three broad steps where it is fixed to ammonia which is incorporated into glutamine and then finally forms glutamate by catalyzation reaction. These three reactions are given below with products formed, reactants, and enzymes involved:

1. Atmospheric nitrogen is the reactant that is reduced to ammonia (product) in this reaction. This reaction is catalyzed by the nitrogenase complex present in bacteria present in legumes:

N2 + 10H+ + 8e- + 16ATP → 2NH4+ + 16ADP + 16Pi + H2.

2. Ammonia (reactant) is incorporated into glutamine (product) in this second reaction which involves glutamine synthetase as catalyst: Glutamate + NH4+ + ATP → glutamine + ADP + Pi + H+.

3. Finally glutamine (final product) is formed by the glutamine (substrate) catalyzed by the glutamate synthase

α-Ketoglutarate + glutamine + NADPH + H+ → 2 glutamate + NADP+.