An O-Acetylserine (Thiol) Lyase cDNA from Spinach

Abstract

Cys biosynthesis represents the essential step of incorporation of reduced sulfur into an organic compound in microorganisms and plants. OAS-TL (EC 4.2.99.8; also called Cys synthase) catalyzes the formation of L-CYS from free or bound sulfide and O-acetyl-L-Ser. Both the substrate O-acetylserine and the product Cys of this reaction are postulated to be involved in the regulation of sulfur uptake and assimilation (Giovanelli et al., 1980; Neuenschwander et al., 1991). OAS-TL has been purified to apparent homogeneity from spinach (Spinacia oleracea L.) leaf extracts (Murakoshi et al., 1985) and spinach chloroplasts (Droux et al., 1992) and consists of

Subcellular Localization of Spinach Cysteine Synthase Isoforms and Regulation of Their Gene Expression by Nitrogen and Sulfur

“…To obtain a comprehensive explanation for the different functional roles of CS isoforms, molecular biologic studies have been initiated. Recently, cDNA clones for the nuclear encoded cytoplasmic, chloroplastic/ plastidic, and putative mitochondrial isoforms have been isolated from various plant species (Romer et al, 1992;Saito et al, 1992Saito et al, , 1993Saito et al, , 1994Hell et al, 1993Hell et al, , 1994Rolland et al, 1993;Youssefian et al, 1993;Noji et al, 1994). We have designated the three genes encoding CS isoforms in spinach as CysA (cytoplasmic) (Saito et al, 1992), CysB (chloroplastic/plastidic) (Saito et al, 1993), and CysC (putative mitochondrial) .…”

Modulation of Cysteine Biosynthesis in Chloroplasts of Transgenic Tobacco Overexpressing Cysteine Synthase [O-Acetylserine(thiol)-Iyase]

“…The presence of CSase isoforms of different subcellular localization in cytoplasm, chloroplasts, and mitochondria has been postulated in plant cells (Schmidt, 1986;Nakamura and Tamura, 1989;Lunn et al, 1990;Rolland et al, 1992). In the last 2 years, cDNA clones of these isoforms have been isolated and characterized (Romer et al, 1992;Saito et al, 1992Saito et al, , 1993Hell et al, 1993;Rolland et al, 1993;Youssefian et al, 1993;Noji et al, 1994). Although this biosynthetic pathway of Cys has been revealed through extensive physiological investigations during the last 2 decades (Schmidt and Jager, 1992, and refs.…”