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Glycine

Glycine functions in excitatory transmission by modulating the actions of glutamate, the major excitatory neurotransmitter in the central nervous system. By nervous system, both the central and peripheral portions of the nervous system are intended. These distinct functions of glycine are mediated by two different types of receptor, each of which is associated with a different class of glycine transporter. The inhibitory actions of glycine are mediated by glycine receptors that are sensitive to the convulsant alkaloid, strychnine. In addition, glycine acts as a co-agonist with glutamate at the NMDA receptor. Glycine is a coagonist of the NMDA receptor with respect to activation of both the glutamate and glycine sites required for channel opening. Drugs like D-cycloserine or 1-aminocyclopropanecarboxylic acid (ACPC) are partial agonists for the glycine binding site of the NMDA receptor. These drugs, also called "partial glycine agonists," can act as agonists or antagonists at the NMDA receptor glycine binding site, depending on their concentration in the brain relative to endogenous glycine. Generally, partial glycine agonists act as antagonists at high concentrations in the brain relative to glycine, without directly blocking the NMDA receptor. Amino carboxylic acids are useful in various applications. Glycine, for example, is widely used as an additive in processed meat, beverages, and in other processed food stuffs. It is also used widely as a raw material for pharmaceuticals, agricultural chemicals, and pesticides. Glycine derivatives such as betaines are known as mild and compatible substances which may be typically co-used in large amounts for the preparation of cosmetic preparations for the cleansing and care of skin and hair. N-(phosphonomethyl)glycine, also known by its common name glyphosate, is a highly effective and commercially important herbicide useful for combating the presence of a wide variety of unwanted vegetation, including agricultural weeds.

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