Which of the following compounds is known to inhibit glutamine synthetase?

Glutamine synthetase is an essential enzyme in the nitrogen metabolism process, catalyzing the conversion of glutamate and ammonia into glutamine. Inhibitors of this enzyme can modulate nitrogen flow and influence various metabolic pathways.

In this context, both glycine and alanine are known to act as inhibitors of glutamine synthetase. Glycine impedes the activity of the enzyme, likely through competitive or allosteric mechanisms. Alanine also plays a similar role and is recognized for its ability to regulate the activity of glutamine synthetase, particularly in specific tissues during times of metabolic need.

Serine does not share this inhibitory effect on glutamine synthetase. Instead, its role is more involved in the synthesis of other biomolecules rather than directly influencing the inhibition of this particular enzyme.

Thus, the presence of both glycine and alanine as inhibitors of glutamine synthetase highlights an important aspect of amino acid metabolism, and their combined effects further emphasize the complexity of metabolic regulation.