Glycine (neurotransmitter)

Glycine acts as an inhibitory neurotransmitter in the central nervous system, especially in the spinal cord and brain stem via the glycine receptor. Compared to GABA, however, it is less significant.

Glycine is added to food as a flavor enhancer. Glycine as well as its sodium salt are generally permitted in the EU as a food additive with the number E 640 without maximum quantity restriction for food, negative health effects are not known. Glycine is, among other things, a component of infusion solutions for parenteral nutrition.

Glycine as a neurotransmitter: Glycine is stored vesicularly in glycinergic neurons. It is released exocytotically after adequate stimulus. It acts via the ionotropic glycine receptor. An inhibitory postsynaptic potential (IPSP) occurs via the opening of ligand-gated chloride channels, which decreases the activity of the downstream neuron. At the NMDA receptor, on the other hand, it has a stimulatory effect at a specific glycine-binding site, in addition to the main agonist glutamate.

A down-regulation of the glycine effect is caused by strychnine, which blocks the binding site of the glycine receptor as an antagonist. Taurine , on the other hand, is an agonist of the glycine receptor. Tetanus toxin inhibits the release of glycine. Tetanus toxin, which has a proteolytic effect, selectively destroys a protein in the salivary vesicles of glycine and GABA that is important for exocytosis, thus blocking the release of the transmitters. The result is the characteristic spasms and convulsions(tetanus=tetanus).

Abnormal accumulation of glycine can lead to glycine encephalopathy.

1. Graefe KH et al. (2016) Graefe KH et al. Central nervous system. In: Graefe KH et al (Eds) Pharmacology and toxicology. Georg Thieme Verlag Stuttgart SS 274-275