Glutamine transport in submitochondrial particles.
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.
Sastrasinh
S
S
Veterans Administration Medical Center, East Orange 07019.
Sastrasinh
M
M
D000138:Acidosis / Q000378:metabolism; D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005972:Glutaminase / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D011865:Radioisotope Dilution Technique; D051381:Rats; D011919:Rats, Inbred Strains; D012402:Rotenone / Q000494:pharmacology; D013367:Submitochondrial Particles / Q000187:drug effects / Q000378:metabolism*; D014316:Tritium
D000596:Amino Acids; D012402:Rotenone; D005973:Glutamine; D014316:Tritium; D005972:Glutaminase