Question

The enzyme glutamine synθse facilitates the use of energy to combine glutamate and ammonia (NH₄⁺), forming glutamine. Which of the following statements best describes the process carried out by glutamine synθse?

1) Glutamine synθse forms glutamine by coupling two endothermic reactions, both of which occur in the enzyme's active site.
2) Glutamine synθse uses an exothermic reaction to drive an endothermic one by catalyzing the formation of a phosphorylated intermediate.
3) Glutamine synθse forms a phosphorylated intermediate by attaching a molecule of ATP to glutamate.
4) Glutamine synθse uses energy to hydrolyze ATP, which then drives the formation of glutamine from glutamate and ammonia.

Answer 1

Glutamine synthetase catalyzes the endothermic reaction that forms glutamine from glutamate and ammonia using the energy from ATP hydrolysis to create a phosphorylated intermediate that results in glutamine formation. Option 4.

Step-by-step explanation:

The enzyme glutamine synthetase catalyzes the formation of glutamine from glutamate and ammonia, an important reaction mainly used for ammonia detoxification. The correct description of the process carried out by glutamine synthetase is that it uses energy to hydrolyze ATP, which then drives the endothermic formation of glutamine from glutamate and ammonia. Specifically, ATP provides the phosphate group that forms phosphorylated glutamate, an intermediate, which then reacts with ammonia to form glutamine, releasing inorganic phosphate. Option 4.

The synthesis of glutamate is also crucial as it involves incorporating inorganic nitrogen (NH4*) into an alpha-keto acid to form an amino acid, which can subsequently be used to produce other amino acids through transamination reactions. Herein, the enzyme ligase category, to which glutamine synthetase belongs, catalyzes the joining of two molecules, exemplifying the critical role of enzymes in biochemical pathways.