Glycyl-glutamine (Glycyl-L-glutamine), as a enzymatic cleavage product of β-endorphin, is apparently an endogenous antagonist of beta-endorphin(1-31) in several systems^[1]. Glycyl-glutamine (Glycyl-L-glutamine) is an activate and stable glutamine-containing neuropeptide over glutamine (Gln)^[2]. In Vitro: Glycyl-glutamine (Glycyl-L-glutamine) is an activate and stable glutamine-containing neuropeptide. Glycyl-glutamine (Glycyl-L-glutamine) has an advantage over free glutamine (Gln)  as growth factors for cell culture during both autoclaving and storage^[2].
In Vivo: Glycyl-glutamine (Glycyl-L-glutamine) (0.3, 0.6, 1.0 and 10.0 nM) can dose-dependently inhibit beta-End-(1-31)-induced hypotension in pentobarbital-anesthetized rats^[1].