Which are the two forms of glutamine dipeptides used in PN admixtures?

• A. L-alanyl-L-glutamine and Glycyl-L-glutamine
• B. L-alanyl-L-glutamine
• C. Glycyl-L-glutamine
• D. None

Answer: (C)

Delivering glutamine in PN is done as dipeptides to improve stability in solution and provide glutamine efficiently after administration. The two dipeptide forms used are L-alanyl-L-glutamine (Ala-Gln) and glycyl-L-glutamine (Gly-Gln). In PN admixtures, free glutamine is unstable, so attaching it to another amino acid creates a stable molecule that is readily hydrolyzed by enzymes in the body to release glutamine where needed, such as in enterocytes and immune cells. Because both dipeptides are used in clinical PN formulations, the correct understanding is that the two forms—Ala-Gln and Gly-Gln—are employed, not just one.