L-glutamine transport in native vesicles isolated from Ehrlich ascites tumor cell membranes.

Native vesicles isolated from Ehrlich ascites tumor cells accumulate glutamine by means of Na(+)-dependent transport systems; thiocyanate seems to be the more effective anion. The apparent affinity constant for the process was 0.38 mM. The Arrhenius plot gave an apparent activation energy of 12.3 kJ/mol. The structural analogs of glutamine, acivicin (2.5 mM) and azaserine (2.5 mM), inhibited the net uptake by 67 and 70%, respectively. The sulfhydryl reagents mersalyl, PCMBS, NEM, and DTNB also inhibited net uptake, suggesting that sulfhydryl groups may be involved in the activity of the carrier protein. A strong inhibition was detected when the vesicles were incubated in the presence of alanine, cysteine, or serine; in addition, histidine, but not glutamate or leucine, had a negative effect on glutamine transport.