Gamma-glutamyl transferase in the cell wall participates in extracellular glutathione salvage from the root apoplast.
The molecular properties and subcellular location of bound gamma-glutamyl transferase (GGT) were studied, and an experimental setup devised to assess its functions in barley roots. Enzyme histochemistry was used to detect GGT activity at tissue level; immunocytochemistry to localize the protein at subcellular level; and modelling studies to investigate its surface charge properties. GGT activity in vivo was measured for the first time. Functions were explored by applying chemical treatments with inhibitors and the thiol-oxidizing drug diamide, performing time-course chromatographic and spectrophotometric analyses on low-molecular-weight thiols. Gamma-glutamyl transferase activity was found to be high in the root apical region and the protein was anchored to root cell wall components, probably by basic amino acid residues. The results show that GGT is essential to the recovery of apoplastic glutathione provided exogenously or extruded by oxidative treatment. It is demonstrated that GGT activity helps to salvage extracellular glutathione and may contribute to redox control of the extracellular environment, thus providing evidence of a functional role for gamma-glutamyl cycle in roots.
Ferretti
M
M
Department of Agricultural Biotechnology, University of Padova, Viale dell'Universita' 16, I-35020 Legnaro (PD), Italy;Department of Biology, University of Padova, Via Trieste 75, I-35100 Padova, Italy;CRIBI Biotech Centre, University of Padova, Via Trieste 75, I-35100 Padova, Italy.
Destro
T
T
Department of Agricultural Biotechnology, University of Padova, Viale dell'Universita' 16, I-35020 Legnaro (PD), Italy;Department of Biology, University of Padova, Via Trieste 75, I-35100 Padova, Italy;CRIBI Biotech Centre, University of Padova, Via Trieste 75, I-35100 Padova, Italy.
Tosatto
S C E
SCE
Department of Agricultural Biotechnology, University of Padova, Viale dell'Universita' 16, I-35020 Legnaro (PD), Italy;Department of Biology, University of Padova, Via Trieste 75, I-35100 Padova, Italy;CRIBI Biotech Centre, University of Padova, Via Trieste 75, I-35100 Padova, Italy.
La Rocca
N
N
Department of Agricultural Biotechnology, University of Padova, Viale dell'Universita' 16, I-35020 Legnaro (PD), Italy;Department of Biology, University of Padova, Via Trieste 75, I-35100 Padova, Italy;CRIBI Biotech Centre, University of Padova, Via Trieste 75, I-35100 Padova, Italy.
Rascio
N
N
Department of Agricultural Biotechnology, University of Padova, Viale dell'Universita' 16, I-35020 Legnaro (PD), Italy;Department of Biology, University of Padova, Via Trieste 75, I-35100 Padova, Italy;CRIBI Biotech Centre, University of Padova, Via Trieste 75, I-35100 Padova, Italy.
Masi
A
A
Department of Agricultural Biotechnology, University of Padova, Viale dell'Universita' 16, I-35020 Legnaro (PD), Italy;Department of Biology, University of Padova, Via Trieste 75, I-35100 Padova, Italy;CRIBI Biotech Centre, University of Padova, Via Trieste 75, I-35100 Padova, Italy.
D002473:Cell Wall / Q000201:enzymology*; D003958:Diamide / Q000494:pharmacology; D005110:Extracellular Space; D005978:Glutathione / Q000378:metabolism*; D001467:Hordeum / Q000201:enzymology*; D018384:Oxidative Stress; D018517:Plant Roots / Q000201:enzymology; D005723:gamma-Glutamyltransferase / Q000737:chemistry / Q000378:metabolism*
D003958:Diamide; D005723:gamma-Glutamyltransferase; D005978:Glutathione