Glycine high affinity transporter

Miller, J. W Kleven, D. T., Domin, B. A., and Fremau Jr., R. T. (1997) Cloned sodium-land chloride-) dependent high affinity transporters for GABA, glycine, proline, betaine, taurine, and creatine, in Neurotransmitter Transporters Structure, Function, and Regulation (Reith, M. E. A., ed.). Humana Press, Totowa, NJ, pp. 101-150. 

Glycine is the major inhibitory neurotransmitter in the spinal cord. Most of the glycine in neurons is synthesized de novo within the nerve terminal from serine by the enzyme serine hydroxymethyltransferase, which requires folic acid. Serine, in turn, is synthesized from the intermediate 3-phosphoglycerate in the glycolytic pathway. The action of glycine is probably terminated via uptake by a high-affinity transporter. 

Substrate specificity is determined by high affinity for the cognate neurotransmitter substrate. However, low affinity uptake does also have a part in the clearance of transmitters from the interstitial space (e.g., in uptake mediated by the extraneuronal monoamine transporter, EMT) and in the intestinal absoiption of glycine and glutamate. It is obvious that there is an evolutionary relation of neurotransmitter transporters and amino acid and cation transporters in epithelia. 

Wilkin GP, Csillag A, Balazs R, Kingsbury AE, Wilson JE, Johnson AL (1981) Localization of high affinity [3H]glycine transport sites in the cerebellar cortex. Brain Res 216 11-33. 

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