Transport of branched-chain amino acids in Corynebacterium glutamicum.
The transport of branched-chain amino acids was characterized in intact cells of Corynebacterium glutamicum ATCC 13032. Uptake and accumulation of these amino acids occur via a common specific carrier with slightly different affinities for each substrate (Km[Ile] = 5.4 microM, Km[Leu] = 9.0 microM, Km[Val] = 9.5 microM). The maximal uptake rates for all three substrates were very similar (0.94 - 1.30 nmol/mg dw.min). The optimum of amino acid uptake was at pH 8.5 and the activation energy was determined to be 80 kJ/mol. The transport activity showed a marked dependence on the presence of Na+ ions and on the membrane potential, but was independent of an existing proton gradient. It is concluded, that uptake of branched-chain amino acid transport proceeds via a secondary active Na+-coupled symport mechanism.
Ebbighausen
H
H
Institut für Biotechnologie, Kernforschungsanlage Jülich GmbH, Federal Republic of Germany.
Weil
B
B
Krämer
R
R
D000597:Amino Acids, Branched-Chain / Q000378:metabolism*; D000693:Anaerobiosis; D001693:Biological Transport, Active; D003352:Corynebacterium / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007532:Isoleucine / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D008564:Membrane Potentials; D012964:Sodium / Q000378:metabolism; D013696:Temperature; D014633:Valine / Q000378:metabolism
D000597:Amino Acids, Branched-Chain; D007532:Isoleucine; D012964:Sodium; D007930:Leucine; D014633:Valine