High-affinity transport of L-glutamine by a plasma membrane preparation from rat brain.
Plasma membrane vesicles prepared from rat brain contain a saturable, high-affinity transport system for L-glutamine that exhibits the following characteristics: (1) The rate of L-glutamine transport is linear up to 200 micrograms/mL membrane protein. (2) Transport of [3H]-L-glutamine is linear with time for at least 10 min, is significantly reduced by lowering the assay temperature to 4 degrees C, and is essentially abolished by the addition of excess unlabeled L-glutamine. (3) The transport rate is optimal in the range of pH 7.4-8.2. (4) The system exhibits a Km for L-glutamine of approximately 1.7 microM and a Vmax of approximately 46 pmol/(min.mg of protein). (5) The system is not highly dependent upon the addition of monovalent or divalent cations. (6) Inhibitor studies reveal that the amino acid amides exhibit the highest affinity for the system and that there is a high specificity for the L-isomers.
Roon
R J
RJ
Department of Biochemistry, University of Minnesota, Minneapolis 55455.
Shofner
S A
SA
Koerner
J F
JF
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001693:Biological Transport, Active; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D066298:In Vitro Techniques; D007536:Isomerism; D007700:Kinetics; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D013379:Substrate Specificity
D000596:Amino Acids; D009419:Nerve Tissue Proteins; D005973:Glutamine