A γ-Glutamyl Transpeptidase-Independent Pathway of Glutathione Catabolism to Glutamate via 5-Oxoproline in Arabidopsis

Thumbnail Image
Date
2008-11-01
Authors
Ohkama-Ohtsu, Naoko
Oikawa, Akira
Zhao, Ping
Xiang, Cheng-Bin
Saito, Kazuki
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Authors
Person
Oliver, David
Professor
Research Projects
Organizational Units
Organizational Unit
Genetics, Development and Cell Biology

The Department of Genetics, Development, and Cell Biology seeks to teach subcellular and cellular processes, genome dynamics, cell structure and function, and molecular mechanisms of development, in so doing offering a Major in Biology and a Major in Genetics.

History
The Department of Genetics, Development, and Cell Biology was founded in 2005.

Related Units

Journal Issue
Is Version Of
Versions
Series
Abstract

The degradation pathway of glutathione (GSH) in plants is not well understood. In mammals, GSH is predominantly metabolized through the γ-glutamyl cycle, where GSH is degraded by the sequential reaction of γ-glutamyl transpeptidase (GGT), γ-glutamyl cyclotransferase, and 5-oxoprolinase to yield glutamate (Glu) and dipeptides that are subject to peptidase action. In this study, we examined if GSH is degraded through the same pathway in Arabidopsis (Arabidopsis thaliana) as occurs in mammals. In Arabidopsis, the oxoprolinase knockout mutants (oxp1-1 and oxp1-2) accumulate more 5-oxoproline (5OP) and less Glu than wild-type plants, suggesting substantial metabolite flux though 5OP and that 5OP is a major contributor to Glu steady-state levels. In the ggt1-1/ggt4-1/oxp1-1 triple mutant with no GGT activity in any organs except young siliques, the 5OP concentration in leaves was not different from that in oxp1-1, suggesting that GGTs are not major contributors to 5OP production in Arabidopsis. 5OP formation strongly tracked the level of GSH in Arabidopsis plants, suggesting that GSH is the precursor of 5OP in a GGT-independent reaction. Kinetics analysis suggests that γ-glutamyl cyclotransferase is the major source of GSH degradation and 5OP formation in Arabidopsis. This discovery led us to propose a new pathway for GSH turnover in plants where GSH is converted to 5OP and then to Glu by the combined action of γ-glutamyl cyclotransferase and 5-oxoprolinase in the cytoplasm.

Comments

This article is from Plant Physiology 148, no. 3 (November 2008): 1603–1613, doi:10.1104/pp.108.125716.

Description
Keywords
Citation
DOI
Copyright
Tue Jan 01 00:00:00 UTC 2008
Collections