L-glutamine is an optically active form of glutamine having L-configuration. It has a role as an nitric oxide synthase inhibitor, a nutraceutical, a micronutrient, a human metabolite, a Saccharomyces cerevisiae metabolite, an Escherichia coli metabolite and a mouse metabolite.

Glutamine is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral, polar amino acid. It is non-essential and conditionally essential in humans, meaning the body can usually synthesize sufficient amounts of it, but in some instances of stress, the body’s demand for glutamine increases, and glutamine must be obtained from the diet.