Question

A) Choose the two enzymes that together catalyze the net reaction:

a-ketoglutarate + NADP(H) + H+ + NH4+ + ATP → Glutamate

b) Why doesn’t the glutamate dehydrogenase reaction contribute much to nitrogen assimilation under normal physiological conditions? (Choose one answer in part b)

Question 10 options:

a) glutamate dehydrogenase

a) glutamine synthetase

a) nitrogenase

a) glutamate synthase

a) α-ketoglutarate dehydrogenase

b)Glutamate dehydrogenase catalyzes the same reaction, but only under conditions of very high NH4+ levels such as agricultural fertilizers since the reaction is unfavorable under standard conditions (ΔGº’ = +30kJ/mol). Under physiological conditions, this reaction deaminates glutamate.

b) Glutamate dehydrogenase needs NADPH for the reaction, which can be limiting under conditions where nitrogen assimilation is needed.

b) Under aerobic conditions, glutamate dehydrogenase has a side reaction with O2 that is wasteful, and therefore organisms prefer to use a different pathway under most physiological conditions.

Expert Answer

Answer 1

glutamine synthetase-glutamate synthase

b)Glutamate dehydrogenase catalyzes the same reaction, but only under conditions of very high NH4+ levels such as agricultural fertilizers since the reaction is unfavorable under standard conditions (ΔGº’ = +30kJ/mol). Under physiological conditions, this reaction deaminates glutamate.

Step-by-step explanation:

The importance of the first reaction you can see that it needs a molecule of ATP in order to create the catalysm, so that´s why that enzyme is called synthetase, since it needs a molecule of ATP to do its work, the other one, the glutamate synthetase, because it does not need the molecule of ATP to do so.

Glutamate can only catalyze the reaction under certain not found in nature regularly conditions, that´s why it doesn´t work as a dehydrogenase.