Transport of phenylalanine into vacuoles isolated from barley mesophyll protoplasts |
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Authors: | U Homeyer G Schultz |
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Institution: | (1) Tierärztliche Hochschule Hannover, Bünteweg 17d, D-3000 Hannover 71, Federal Republic of Germany |
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Abstract: | The energy-dependent transport of phenylalanine into isolated vacuoles of barley (Hordeum vulgare L.) mesophyll protoplasts has been studied by silicone-layer floatation filtering. The uptake of this aromatic amino acid into the vacuolar compartment is markedly increased by MgATP, showing saturation kinetics; the K
m values were 0.5 mM for MgATP and 1.2 mM for phenylalanine. V
max for phenylalanine transport was estimated to 140 nmol phenylalanine·(mg·Chl)-1·h-1. The transport shows a distinct pH optimum at 7.3 and is markedly inhibited by 40 mM nitrate. Azide (1 mM) and vanadate (400 M) had no or little effect on rates of transport while p-fluorophenylalanine seemed to be an effective inhibitor, indicating a possible competition at an amino-acid carrier. Ionophores such as valinomycin, nigericin or gramicidin were strong inhibitors of phenylalanine transport, indicating that this process is coupled to both the transmembrane pH gradient ( pH) and the transmembrane potential (![Delta](/content/l3228010741m7590/xxlarge916.gif) ).Abbreviations and symbols BSA
bovine serum albumin
- Chl
chlorophyll
- Hepes
4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
- pH
transmembrane pH gradient
- ![Delta](/content/l3228010741m7590/xxlarge916.gif)
transmembrane potential |
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Keywords: | ATPase(Mg-) (Hordeum (phenylalanine transport) Phenylalanine Transport (phenylalanine) Vacuole (phenylalanine uptake) |
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