Electrogenic glutamine uptake by Peptostreptococcus anaerobius and generation of a transmembrane potential.
Peptostreptococcus anaerobius converted glutamine stoichiometrically to ammonia and pyroglutamic acid, and the Eadie-Hofstee plot of glutamine transport was biphasic. High-affinity, sodium-dependent glutamine transport (affinity constant [Kt] of 1.5 microM) could be driven by the chemical gradient of sodium, and more than 20 mM sodium was required for half-maximal velocity. High-affinity glutamine transport was not stimulated or inhibited by a membrane potential (delta psi). Low-affinity glutamine transport had a rate which was directly proportional to the external glutamine concentration, required less than 100 microM sodium, and was inhibited strongly by a delta psi. Cells which were treated with N,N-dicyclohexylcarbodiimide to inhibit the F1F0 ATPase still generated a delta psi but did so only if the external glutamine concentration was greater than 15 mM. Low-affinity glutamine uptake could not be saturated by as much as 200 mM glutamine, but glutamine-1 accounts for only a small fraction of the total glutamine at physiological pH values (pH 6 to 7). On the basis of these results, it appeared that the low-affinity glutamine transport was an electrogenic mechanism which was converting a chemical gradient of glutamine-1 into a delta psi. Other mechanisms of delta psi generation (electrogenic glutamine-pyroglutamate or -ammonium exchange) could not be demonstrated.
Beck
B J
BJ
Section of Microbiology, Cornell University, Ithaca, New York 14853.
Russell
J B
JB
D001692:Biological Transport / Q000187:drug effects; D002250:Carbon Radioisotopes; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D005973:Glutamine / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology*; D008985:Monensin / Q000494:pharmacology; D010462:Peptostreptococcus / Q000378:metabolism / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D012458:Salicylanilides / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D013997:Time Factors; D014325:Tromethamine / Q000494:pharmacology
D002250:Carbon Radioisotopes; D012458:Salicylanilides; D014325:Tromethamine; D005973:Glutamine; D012965:Sodium Chloride; D004024:Dicyclohexylcarbodiimide; D008985:Monensin; D012964:Sodium; C003390:3,3',4',5-tetrachlorosalicylanilide; D011188:Potassium