Should L-glutamine or GlutaMAX be used as substrate in XF assay media?

Glutamine is the preferred and recommended substrate to include in XF assays.  GlutaMAX, a stable dipeptide (L-alanine-L-glutamine) is not recommended for XF assays as the conversion of GlutaMAX to free glutamine may become a rate limiting step in the overall kinetics of glutamine oxidation by mitochondria, and may lead to reduced assay signal.