What is the role of ATP during the synthesis of glutamine fr

What is the role of ATP during the synthesis of glutamine from glutamate?

a.Hydrolysis of ATP drives the endergonic reaction

b.ATP provides a phosphoryl group, creating a good leaving group that can be displaced by ammonia

c.Interaction with ATP increases the efficiency of glutamine synthetase

d.Hydrolysis of ATP supplies protons

e. More than one answer is correct

Solution

Answer (e) More than one answer is correct (both ‘b’ and ‘c’ options are correct)

Glutamine synthetase (GS) catalyze the synthesis of glutamine from glutamate, which is the ATP-dependent condensation of glutamate with ammonia to yield glutamine.

b) ATP provides a phosphoryl group, creating a good leaving group that can be displaced by ammonia:

Both ATP and glutamate bind at active site of enzyme at different pocket. GS hydrolyze ATP and transfer Pi (inorganic phosphate) to glutamate to form ADP and an intermediate, -glutamyl phosphate, which reacts with ammonia, forming glutamine and inorganic phosphate.

c) Interaction with ATP increases the efficiency of glutamine synthetase:

Hydrolysis of ATP provide ADP and Pi. ADP introduces a conformational change in GS that stabilizes the -glutamyl phosphate moiety. Ammonium binds strongly to GS only if the -glutamyl phosphate intermediate is present.