Meister cycle

Concerning transport of amino acids across the brain-blood barrier, the possible role of the Meister cycle< > seems very attractive in the y-glutamyl cycle, glutathione acts as the amino acid carrier and the concentration of glutathione has been found to be significantly higher in the newborn brain than in the adult. 

Meister A. 1981. On the cycles of glutathione metabolism and transport. Curr Top Cell Regul 18 21-57. 

On the Cycles of Glutathione Metabolism and Transport Alton Meister... 

Gly + y-glutamyl amino acid. The products are transported into the cell and are cleaved, the Clys-Gly to Gly and Cys, and the y-glutamyl amino acid to 5-oxoproline and the amino acid. S-Oxoproline is converted to glutamic acid, so that the y-glutamyl cycle can repeat. [A.Meister Science 220 (1983) 472-477]... 

Meister (1973) has suggested that transport of many amino acids in the kidney and probably in other tissues could be mediated by a cycle of enzymatic reactions involving the membrane-bound enzyme y-glu-tamyl transpeptidase as a binding site for amino acids. Meister does not, however, exclude the possibility of other transport pathways for the active transport of amino acids, nor is he able to define the extent to which the cycle could function. At the present time, the identification of the y-glutamyl transpeptidase cycle as a mediator of amino acid transport represents only an interesting hypothesis, and attempts to correlate y-glutamyl transpeptidase activity with amino acid transport activity have been fruitless. 

Wellner, V.P., Sekura, R., Meister, A. andLarsson, A. (1974), Glutathione synthetase deficiency, an inborn error of metabolism involving the y-glutamyl cycle in patients with 5-oxoprolinuria (pyroglutamic aciduria). Proc. Natl. Acad. Sci. U.S.A., 71, 2505. 

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