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Leucine Transport in Cells Isolated from Cold-Hardened and Nonhardened Winter Rye

Authors :
Leslie R. Barran
Jas Singh
Source :
Plant Physiology. 69:793-797
Publication Year :
1982
Publisher :
Oxford University Press (OUP), 1982.

Abstract

The properties of the leucine transport systems of cells isolated from dark-grown cold-hardened and nonhardened winter rye (Secale cereale L. cv. Puma) epicotyls were remarkably similar. After 1 hour of incubation, leucine was accumulated in the cells 80- to 100-fold above that of the external medium, but the transported leucine was not metabolized. Approximately one-third of the accumulated leucine was present in the vacuole after 40 minutes of incubation. At 25 degrees C, efflux of leucine from the vacuole was 6 to 10 times slower than it was from the cytoplasm, while at 5 degrees C efflux from the cells was inhibited.The apparent K(m) and V(max) for leucine uptake for both types of cells were of the order of 20 to 60 micromolar and 0.5 to 1.3 nanomoles per minute per 10(6) cells. The pH and temperature optima for both types of cells were 5 and 25 degrees C, respectively. The leucine transport system for these cells was relatively specific for amino acids lacking either bulky or charged groups on the amino acid side chains.Arrhenius plots for leucine uptake by hardened and nonhardened cells showed discontinuities at 13 degrees C, and the energies of activation were similar. The results suggests that biochemical changes which occur in rye cells upon cold hardening did not result in an observable perturbation of the properties of the leucine transport system.

Details

ISSN :
15322548 and 00320889
Volume :
69
Database :
OpenAIRE
Journal :
Plant Physiology
Accession number :
edsair.doi.dedup.....84791d64388667bca0869ff44841cc05
Full Text :
https://doi.org/10.1104/pp.69.4.793