APA Dictionary of Psychology

n. an amino acid that serves as one of the two major inhibitory neurotransmitters in the central nervous system (particularly the spinal cord), the other being gamma-aminobutyric acid (GABA). Glycine is also a cotransmitter with glutamate at excitatory NMDA receptors. Glycine synthesis occurs via two different pathways; in the most important of these, glycine is synthesized from the amino acid serine in a single reaction catalyzed by the enzyme serine hydroxymethyltransferase.