L-glutamine is an essential amino acid required by virtually all mammalian and insect cells grown in culture. It is a crucial component of many cell culture media and serves as a major energy source for cells in culture. L-glutamine is very stable as a dry powder and as a frozen solution. However, in liquid media or stock solutions, L-glutamine can degrade relatively rapidly. L-glutamine is also more labile in cell culture solution than other amino acids.
Dipeptide derivatives of L-glutamine (stable glutamine) prevent the intramolecular cyclisation reaction associated with solutions of L-glutamine. These derivatives are therefore stable in solution and allow the formulation of cell culture media containing L-glutamine that may be stored at 4 °C for extended periods. Solutions containing these derivatives can even be autoclaved without appreciable degradation of the product (30 minutes at 121 °C results in <5% loss of the product).
The dipeptide derivatives are metabolised within the cells to yield L-glutamine plus the second amino acid. This results in more consistent delivery of L-glutamine to cells and avoids toxic build-up of ammonia in cell cultures. This feature can be especially important for ammonia-sensitive cell lines.