Absence of a role of gamma-glutamyl transpeptidase in the transport of amino acids by rat renal brushborder membrane vesicles

1984 ◽  
Vol 80 (2) ◽  
pp. 167-173 ◽  
Author(s):  
Betty Y. L. Hsu ◽  
John W. Foreman ◽  
Susan M. Corcoran ◽  
Kristina Ginkinger ◽  
Stanton Segal
Keyword(s):  
Amino Acids ◽  
Membrane Vesicles ◽  
Gamma Glutamyl Transpeptidase ◽  
Gamma Glutamyl ◽  
Glutamyl Transpeptidase

scholarly journals The effect of azaserine on glutamine uptake by rat renal brush-border membranes

1980 ◽  
Vol 192 (1) ◽  
pp. 119-126 ◽  
Author(s):  
B Y Hsu ◽  
C M Marshall ◽  
P D McNamara ◽  
S Segal
Keyword(s):  
Brush Border ◽  
Membrane Vesicles ◽  
Competitive Inhibitor ◽  
Transport Systems ◽  
Gamma Glutamyl Transpeptidase ◽  
Gamma Glutamyl ◽  
Transport Inhibition ◽  
Renal Brush Border Membrane ◽  
Glutamyl Transpeptidase ◽  
Renal Brush Border

Azaserine added directly to isolated rat renal brush-border membrane vesicles inhibits uptake of L-glutamine. Azaserine acts as a non-competitive inhibitor of the low-Km system for glutamine transport, but has no effect on the high-Km system. Preincubation of the vesicles with azaserine at 37 degrees C min is not required for transport inhibition to occur, although it is a requirement for gamma-glutamyl transpeptidase inhibition. Removal of azaserine from the vesicle preparation by repeated resuspensions in buffer results in a reversal of the transport inhibition but not in reversal of enzyme inhibition. Azaserine also inhibits vesicle uptake of L-proline and alpha-methyl D-glucoside, indicating a generalized effect on membrane transport systems. The data cast doubt on the postulate that gamma-glutamyl transpeptidase might act as the carrier mechanism for glutamine reabsorption by renal cortical cells.

Regulation of cellular glutathione

1989 ◽  
Vol 257 (4) ◽  
pp. L163-L173 ◽  
Author(s):  
S. M. Deneke ◽  
B. L. Fanburg
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cultured Cells ◽  
Feedback Inhibition ◽  
Reductase Activity ◽  
Transport Systems ◽  
Synthetase Activity ◽  
Gamma Glutamyl Transpeptidase ◽  
Gamma Glutamyl ◽  
Glutamyl Transpeptidase

In addition to its participation in a variety of other biochemical reactions, glutathione (GSH) is a major antioxidant. It is regularly generated intracellularly from its oxidized form by glutathione reductase activity that is coupled with a series of interrelated reactions. Synthesis of GSH also takes place intracellularly by a two-step reaction, the first of which is catalyzed by rate-limiting gamma-glutamylcysteine synthetase activity. Intracellular substrates for GSH are provided both by direct amino acid transport and by a gamma-glutamyl transpeptidase reaction that salvages circulating GSH by coupling the gamma-glutamyl moiety to a suitable amino acid acceptor for transport into the cell. Although the liver is a net synthesizer of circulating GSH, organs such as the kidney salvage GSH through the gamma-glutamyl transpeptidase reaction. Intracellular GSH may be consumed by GSH transferase reactions that conjugate GSH with certain xenobiotics. Elevation of cellular GSH levels in cultured cells in response to hyperoxia or electrophilic agents such as diethylmaleate is coupled with an increase in activity of the Xc- transport system for the amino acids cystine and glutamate. Strategies may be developed for protection against oxidant injury by enhancement of transport systems for precursor amino acids of GSH or by providing substrate that circumvents feedback inhibition of GSH synthesis.

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