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Roles of the enantioselective glutathione S-transferases in cleavage of beta-aryl ether.

ABSTRACT: Cleavage of the beta-aryl ether linkage is the most important process in lignin degradation. Here we characterize the three tandemly located glutathione S-transferase (GST) genes, ligF, ligE, and ligG, from low-molecular-weight lignin-degrading Sphingomonas paucimobilis SYK-6, and we describe the actual roles of these genes in the beta-aryl ether cleavage. Based on the identification of the reaction product by electrospray ionization-mass spectrometry, a model compound of beta-aryl ether, alpha-(2-methoxyphenoxy)-beta-hydroxypropiovanillone (MPHPV), was transformed by LigF or LigE to guaiacol and alpha-glutathionyl-beta-hydroxypropiovanillone (GS-HPV). This result suggested that LigF and LigE catalyze the nucleophilic attack of glutathione on the carbon atom at the beta position of MPHPV. High-pressure liquid chromatography-circular dichroism analysis indicated that LigF and LigE each attacked a different enantiomer of the racemic MPHPV preparation. The ligG gene product specifically catalyzed the elimination of glutathione from GS-HPV generated by the action of LigF. This reaction then produces an achiral compound, beta-hydroxypropiovanillone, which is further degraded by this strain. Disruption of the ligF, ligE, and ligG genes in SYK-6 showed that ligF is essential to the degradation of one of the MPHPV enantiomers, and the alternative activities which metabolize the substrates of LigE and LigG are present in this strain.

SUBMITTER: Masai E

PROVIDER: S-EPMC150126 | biostudies-literature | 2003 Mar

REPOSITORIES: biostudies-literature

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Roles of the enantioselective glutathione S-transferases in cleavage of beta-aryl ether.

Masai Eiji E Ichimura Atsushi A Sato Yusuke Y Miyauchi Keisuke K Katayama Yoshihiro Y Fukuda Masao M

Journal of bacteriology 20030301 6

Cleavage of the beta-aryl ether linkage is the most important process in lignin degradation. Here we characterize the three tandemly located glutathione S-transferase (GST) genes, ligF, ligE, and ligG, from low-molecular-weight lignin-degrading Sphingomonas paucimobilis SYK-6, and we describe the actual roles of these genes in the beta-aryl ether cleavage. Based on the identification of the reaction product by electrospray ionization-mass spectrometry, a model compound of beta-aryl ether, alpha- ...[more]

PMID: 12618439

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Project description:Glutathione transferases (GSTs) represent a widespread multigenic enzyme family able to modify a broad range of molecules. These notably include secondary metabolites and exogenous substrates often referred to as xenobiotics, usually for their detoxification, subsequent transport or export. To achieve this, these enzymes can bind non-substrate ligands (ligandin function) and/or catalyze the conjugation of glutathione onto the targeted molecules, the latter activity being exhibited by GSTs having a serine or a tyrosine as catalytic residues. Besides, other GST members possess a catalytic cysteine residue, a substitution that radically changes enzyme properties. Instead of promoting GSH-conjugation reactions, cysteine-containing GSTs (Cys-GSTs) are able to perform deglutathionylation reactions similarly to glutaredoxins but the targets are usually different since glutaredoxin substrates are mostly oxidized proteins and Cys-GST substrates are metabolites. The Cys-GSTs are found in most organisms and form several classes. While Beta and Omega GSTs and chloride intracellular channel proteins (CLICs) are not found in plants, these organisms possess microsomal ProstaGlandin E-Synthase type 2, glutathionyl hydroquinone reductases, Lambda, Iota and Hemerythrin GSTs and dehydroascorbate reductases (DHARs); the four last classes being restricted to the green lineage. In plants, whereas the role of DHARs is clearly associated to the reduction of dehydroascorbate to ascorbate, the physiological roles of other Cys-GSTs remain largely unknown. In this context, a genomic and phylogenetic analysis of Cys-GSTs in photosynthetic organisms provides an updated classification that is discussed in the light of the recent literature about the functional and structural properties of Cys-GSTs. Considering the antioxidant potencies of phenolic compounds and more generally of secondary metabolites, the connection of GSTs with secondary metabolism may be interesting from a pharmacological perspective.

Dataset Information

Roles of the enantioselective glutathione S-transferases in cleavage of beta-aryl ether.

Publications

Roles of the enantioselective glutathione S-transferases in cleavage of beta-aryl ether.

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