Possible role of glutathione in transport processes.

Abstract

A discussion of the possible function of glutathione in transport processes should consider two structural features of the molecule; namely the presence of a SH group and the presence of a γ-glutamyl group. Glutathione is present in all mammalian tissues and cells. Its concentration in the kidney was reported as 2 to 4 mM20. Concentrations as high as 10 to 12 mM, however, have heen found in some other tissues62, 84.In spite of its “ubiquitous” presence the role of glutathione is not yet sufficiently understood. Most of the studies on glutathione have centered on its function in maintaining sulfhydryl groups of proteins in a reduced state, on its protection of cell membranes against an oxidative stress, and on its role in detoxification of foreign compounds. Glutathione has also been credited with a coenzyme function in several enzymatic reactions. All these functions are dependent on the presence of an intact sulfhydryl group. The possible role of the γ-glutamyl group of glutathione has attracted less attention. This discussion will be limited to the enzymology of the γ-glutamyl group. Some experiments, however, will be reviewed in which the evidence can be taken as supporting the involvement of either the γ-glutamyl group or the SH group in the transport of amino acids.