Glycine

Glycine is a principal inhibitory amino acid in the brainstem and spinal cord that regulates excitatory neurotransmission in much the same way as GABA. Glycine, much like GABA and taurine, can become elevated to compensate for elevations in excitatory neurotransmitters, primarily, glutamate and aspartic acid. This non-essential amino acid is common in protein-based foods, and can be synthesized metabolically from a number of different amino acids, including serine and threonine.; Curiously, glycine is a necessary cofactor in the activation of the glutamate receptor, NMDA. It seems paradoxical that a primarily inhibitory amino acid facilitates the activation of an excitatory receptor. It has been postulated that glycine’s inhibitory and excitatory actions are part of the many checks and balances the body has for regulating neurotransmission.