AJP - Renal Physiology, Vol 257, Issue 6 1050-F1058, Copyright © 1989 by American Physiological Society

ARTICLES

Glutamine transport in submitochondrial particles

S. Sastrasinh and M. Sastrasinh
Veterans Administration Medical Center, East Orange 07019.

Glutamine transport was studied in submitochondrial particles (SMP) to avoid interference from glutamine metabolism. Phosphate-dependent glutaminase activity in SMP was only 0.04% of that in intact mitochondria. The uptake of glutamine in SMP represented both the transport into vesicles and membrane binding (about one-third of total uptake). Sulfhydryl reagents inhibited glutamine uptake in SMP. The uptake of L-[3H]glutamine increased more than twofold in SMP preloaded with 1 mM L-glutamine, an effect that was not seen with 1 mM D-glutamine. The uptake of L-[3H]glutamine was inhibited in the presence of either L-glutamine or L-alanine in the incubation medium. Other amino acids did not inhibit glutamine uptake. Alanine was also shown to trans-stimulate glutamine transport in SMP and cis-inhibit glutamine transport in both SMP and intact mitochondria. Glutamine transport showed a positive cooperativity effect with a Hill coefficient of 1.45. Metabolic acidosis increased the affinity of the transporter for glutamine without any change in other kinetic parameters. These data indicated that mitochondrial glutamine transport occurs via a specific carrier with multiple binding sites and that the transport of glutamine into mitochondria has an important role in increased ammoniagenesis during metabolic acidosis.

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