Functional Divergence in the Glutathione Transferase Superfamily in Plants

Abstract

Searches with the human Omega glutathione transferase (GST) identified two outlying groups of the GST superfamily in Arabidopsis thaliana which differed from all other plant GSTs by containing a cysteine in place of a serine at the active site. One group consisted of four genes, three of which encoded active glutathionedependent dehydroascorbate reductases (DHARs). Two DHARs were predicted to be cytosolic, whereas the other contained a chloroplast targeting peptide. The DHARs were also active as thiol transferases but had no glutathione conjugating activity. Unlike most other GSTs, DHARs were monomeric. The other class of GST comprised two genes termed the Lambda GSTs (GSTLs). The recombinant GSTLs were also monomeric and had glutathione-dependent thiol transferase activity. One GSTL was cytosolic, whereas the other was chloroplasttargeted. When incubated with oxidized glutathione, the putative active site cysteine of the GSTLs and cytosolic DHARs formed mixed disulfides with glutathione, whereas the plastidic DHAR formed an intramolecular disulfide. DHAR S-glutathionylation was consistent with a proposed catalytic mechanism for dehydroascorbate reduction. Roles for the cytosolic DHARs and GSTLs as antioxidant enzymes were also inferred from the induction of the respective genes following exposure to chemicals and oxidative stress.

Glutathione S-Transferase Omega 1-1 Is a Target of Cytokine Release Inhibitory Drugs and May Be Responsible for Their Effect on Interleukin-1औ Posttranslational Processing

“…As noted above, the Omega class of GSTs is evolutionarily conserved in plants. The Arabidopsis thaliana genome, for example, contains at least five separate genes encoding GST family members possessing the conserved CPF active center motif (90). Although biological function of the plant enzymes also remains to be elucidated, conservation within both the plant and animal kingdoms suggests that this family of enzymes serves an important function worthy of further investigation.…”

Characterization of PAP1-upregulated Glutathione S-transferase genes in Arabidopsis thaliana

“…Based on gene organization (intron number and position), sequence similarity, and the conservation of specific residues, plant GSTs can be classified into the following 5 classes: zeta, theta, tau, phi, and lambda (Dixon et al 2002a). Recently, a new group of GST-like proteins with glutathione-dependent dehydroascorbate reductase (DHAR) activity has been classified in Arabidopsis and some other plant species (Dixon et al 2002b;Frova 2003).…”

Ağır Metallerin <i>Pinus brutia</i> Ten. İğne Yapraklarında, Glutatyon S-Transferaz Enzimleri Üzerindeki Tekil ve Bazı Bütünleşik İnhibisyonları

“…Çözünür glutatyon S-konjugeleri pek çok metabolik detoksifikasyon işlemlerine ve oksidatif baskıya karşı devreye giren mekanizmalara katılan ve bitkilerin ikincil metabolizmaları dahilinde sayılan Faz-II enzimlerini içeren kofullarda bulunurlar [14,15,16]. Bu sitozolik savunma sistemi, normal metabolizma sürecinde açığa çıkan elektrofilleri, GSH molekülünü ya kosubstrat ya da koenzim olarak kullanmak yoluyla bağlar [17]. Bitki GST'lerinin dört grubu da GSH'ın tiyolat formuyla konjugasyon, peroksidaz ve izomeraz reaksiyonları gerçekleştirecek şekilde serin aktif bölgesinde bir serin yapısı bulundurmaktadırlar.…”