Uptake and utilization of L-glutamine by human lymphoid cells; relationship to γ-glutamyl transpeptidase activity
Saccharomyces cerevisiae Proteins
Initial rates of glutamine uptake were studied in human lymphoid cell lines whose γ-glutamyl transpeptidase activities vary from 93 to 11,300 units/mg. In general, glutamine was transported at lower rates than other amino acids (met, phe, leu) in all cell lines studied. A cell line with very high transpeptidase activity exhibited an increased rate of glutamine uptake as compared to other amino acids, and a markedly decreased intracellular concentration of glutamine. In all cell lines transported glutamine was extensively (80%) converted to glutamate. Treatment of cells with 6-diazo-5-oxo-L-norleucine (DON) decreased transpeptidase and conversion of transported glutamine to glutamate by about 80%. Inhibition of glutamine transport was less pronounced (0-20%). The findings indicate that transported glutamine does not equilibrate with glutamine in the intracellular pool, but may enter a separate pool in which it is rapidly converted to glutamate. © 1977.
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