Uptake of glutamine by the scutellum of germinating barley grain

Tuomas Sopanen (Corresponding Author), Eila Väisänen

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Scutella separated from germinating grains of barley (Hordeum vulgare L. cv Himalaya) took up [14C]glutamine at an initial rate of about 10 micromoles·gram−1·hour−1 in the standard assay conditions (pH 5, 30°C, 1 millimolar glutamine). Inhibition by unlabeled glutamine and by dinitrophenol indicated that about 95% of the uptake was due to carrier-mediated active transport. The pH optimum of the uptake was 5, and after correction for a nonmediated component the uptake appeared to conform to Michaelis-Menten kinetics with an apparent Km of about 2 millimolar and a Vmax of about 25 micromoles·gram−1·hour−1.

The uptake of glutamine was inhibited by all of the 18 amino acids tested; the mode of inhibition was studied only with proline and was competitive. Eight of the ten amino acids tested at high concentrations appeared to be able to inhibit the mediated uptake of glutamine virtually completely. However, when the inhibitory effect of asparagine was extrapolated to an infinitely high concentration of asparagine, about 24% of the mediated uptake of glutamine remained uninhibited. These results suggest that glutamine is taken up by two (or more) rather unspecific amino acid uptake systems, the minor one having no affinity for asparagine.

Glutamine and alanine could completely inhibit the mediated uptake of 1 millimolar leucine, but about 12% of the mediated uptake appeared to be uninhibitable by asparagine. Furthermore, the ratio of the mediated uptake of glutamine to that of leucine changed from 0.9 to 1.7 between days 1 and 3 of germination. These results give further support for the presence of two unspecific amino acid uptake systems in barley scutella.

Original languageEnglish
Pages (from-to)684 - 689
Number of pages6
JournalPlant Physiology
Volume78
Issue number4
DOIs
Publication statusPublished - 1985
MoE publication typeNot Eligible

Fingerprint

Hordeum
Glutamine
glutamine
barley
uptake mechanisms
Asparagine
asparagine
Amino Acids
amino acids
Leucine
leucine
Dinitrophenols
Active Biological Transport
Germination
enzyme kinetics
Proline
active transport
Alanine
alanine
Hordeum vulgare

Cite this

Sopanen, Tuomas ; Väisänen, Eila. / Uptake of glutamine by the scutellum of germinating barley grain. In: Plant Physiology. 1985 ; Vol. 78, No. 4. pp. 684 - 689.
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abstract = "Scutella separated from germinating grains of barley (Hordeum vulgare L. cv Himalaya) took up [14C]glutamine at an initial rate of about 10 micromoles·gram−1·hour−1 in the standard assay conditions (pH 5, 30°C, 1 millimolar glutamine). Inhibition by unlabeled glutamine and by dinitrophenol indicated that about 95{\%} of the uptake was due to carrier-mediated active transport. The pH optimum of the uptake was 5, and after correction for a nonmediated component the uptake appeared to conform to Michaelis-Menten kinetics with an apparent Km of about 2 millimolar and a Vmax of about 25 micromoles·gram−1·hour−1. The uptake of glutamine was inhibited by all of the 18 amino acids tested; the mode of inhibition was studied only with proline and was competitive. Eight of the ten amino acids tested at high concentrations appeared to be able to inhibit the mediated uptake of glutamine virtually completely. However, when the inhibitory effect of asparagine was extrapolated to an infinitely high concentration of asparagine, about 24{\%} of the mediated uptake of glutamine remained uninhibited. These results suggest that glutamine is taken up by two (or more) rather unspecific amino acid uptake systems, the minor one having no affinity for asparagine. Glutamine and alanine could completely inhibit the mediated uptake of 1 millimolar leucine, but about 12{\%} of the mediated uptake appeared to be uninhibitable by asparagine. Furthermore, the ratio of the mediated uptake of glutamine to that of leucine changed from 0.9 to 1.7 between days 1 and 3 of germination. These results give further support for the presence of two unspecific amino acid uptake systems in barley scutella.",
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Uptake of glutamine by the scutellum of germinating barley grain. / Sopanen, Tuomas (Corresponding Author); Väisänen, Eila.

In: Plant Physiology, Vol. 78, No. 4, 1985, p. 684 - 689.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Uptake of glutamine by the scutellum of germinating barley grain

AU - Sopanen, Tuomas

AU - Väisänen, Eila

PY - 1985

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N2 - Scutella separated from germinating grains of barley (Hordeum vulgare L. cv Himalaya) took up [14C]glutamine at an initial rate of about 10 micromoles·gram−1·hour−1 in the standard assay conditions (pH 5, 30°C, 1 millimolar glutamine). Inhibition by unlabeled glutamine and by dinitrophenol indicated that about 95% of the uptake was due to carrier-mediated active transport. The pH optimum of the uptake was 5, and after correction for a nonmediated component the uptake appeared to conform to Michaelis-Menten kinetics with an apparent Km of about 2 millimolar and a Vmax of about 25 micromoles·gram−1·hour−1. The uptake of glutamine was inhibited by all of the 18 amino acids tested; the mode of inhibition was studied only with proline and was competitive. Eight of the ten amino acids tested at high concentrations appeared to be able to inhibit the mediated uptake of glutamine virtually completely. However, when the inhibitory effect of asparagine was extrapolated to an infinitely high concentration of asparagine, about 24% of the mediated uptake of glutamine remained uninhibited. These results suggest that glutamine is taken up by two (or more) rather unspecific amino acid uptake systems, the minor one having no affinity for asparagine. Glutamine and alanine could completely inhibit the mediated uptake of 1 millimolar leucine, but about 12% of the mediated uptake appeared to be uninhibitable by asparagine. Furthermore, the ratio of the mediated uptake of glutamine to that of leucine changed from 0.9 to 1.7 between days 1 and 3 of germination. These results give further support for the presence of two unspecific amino acid uptake systems in barley scutella.

AB - Scutella separated from germinating grains of barley (Hordeum vulgare L. cv Himalaya) took up [14C]glutamine at an initial rate of about 10 micromoles·gram−1·hour−1 in the standard assay conditions (pH 5, 30°C, 1 millimolar glutamine). Inhibition by unlabeled glutamine and by dinitrophenol indicated that about 95% of the uptake was due to carrier-mediated active transport. The pH optimum of the uptake was 5, and after correction for a nonmediated component the uptake appeared to conform to Michaelis-Menten kinetics with an apparent Km of about 2 millimolar and a Vmax of about 25 micromoles·gram−1·hour−1. The uptake of glutamine was inhibited by all of the 18 amino acids tested; the mode of inhibition was studied only with proline and was competitive. Eight of the ten amino acids tested at high concentrations appeared to be able to inhibit the mediated uptake of glutamine virtually completely. However, when the inhibitory effect of asparagine was extrapolated to an infinitely high concentration of asparagine, about 24% of the mediated uptake of glutamine remained uninhibited. These results suggest that glutamine is taken up by two (or more) rather unspecific amino acid uptake systems, the minor one having no affinity for asparagine. Glutamine and alanine could completely inhibit the mediated uptake of 1 millimolar leucine, but about 12% of the mediated uptake appeared to be uninhibitable by asparagine. Furthermore, the ratio of the mediated uptake of glutamine to that of leucine changed from 0.9 to 1.7 between days 1 and 3 of germination. These results give further support for the presence of two unspecific amino acid uptake systems in barley scutella.

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