Comparison of properties of leaf and root glutathione reductases from spinach

Abstract

Glutathione reductase (GR; EC 1.6.4.2) was purified from spinach roots (rGR) to homogeneity in terms of SDS‐PAGE, and its properties were compared with those of the enzyme from spinach leaves (IGR). The two enzymes had similar native molecular (118000) and subunit masses (58000) and immunochemical properties, but different pH optima (ca pH 7.8 for IGR, ca pH 7.2 for rGR) and amino acid compositions. Peptide maps of two GRs showed that they differed from each other. The N‐terminal amino acid of the IGR was glycine and that of the rGR was blocked. The partial amino acid sequence of the N‐terminal region of the IGR was determined to the 11 th residue and it was found that the sequence of 8 amino acids of the IGR had 100% homology with that of the putative chloroplast GR from Arabidopsis and pea.

Selenium Speciation of Soil/Sediment Determined with Sequential Extractions and Hydride Generation Atomic Absorption Spectrophotometry

“…Research has also found that 0.1 M potassium phosphate is an effective extractant for plant protein (36) and that it extracts seleniferous proteins if present in nondecomposed seleniferous plant material in soil. We achieved >95% spike recovery rates by the HGAAS speciation procedure when we spiked [1 µg of each Se species (g of soil) -1 ] a nonseleniferous soil with selenate, selenite, and selenomethionine and extracted with P-buffer.…”

Oxidative stress and antioxidant systems in Guava (Psidium guajava L.) fruits during ripening

“…Moreover, GSSG increased by 3 per cent in L-49 and by 6 per cent in Hisar Safeda from IG stage to ripe stage indicating an increase in cellular oxidative status during ripening. Glutathione system has been reported to be involved directly in maintaining a low redox potential and thus a highly reduced intracellular environment (Tanaka et al 1994). Tomato and saskatoon fruit have also been reported to respond to the increase in oxidative stress by increasing reduced and oxidized glutathione during development (Rogiers et al 1998;Andrews et al, 2004).…”

Oxidative Stress Results in Increased Sinks for Metabolic Energy during Aging and Sprouting of Potato Seed-Tubers

“…This is facilitated by an age-dependent increase in GRase activity (Table VI), which maintains more than 90% of cellular glutathione in the reduced form (Tanaka et al, 1994) via the NADPH-dependent reduction of GSSG (Carlberg and Mannervik, 1985). The increased synthesis of GSH during aging and its regeneration from GSSG necessitate greater consumption of ATP (Hell and Bergmann, 1988) SEED-TUBER AGE (months) and NADPH, respectively, and thus constitute increased sinks for metabolic energy in older tubers.…”

“…Isolated mitochondria were washed with BSA-free buffer (Kumar and Knowles, 1996) and solubilized with 0.2% Triton X-100. Proteins were electroblotted to nitrocellulose as described by Luethy et al (1993), and GRase was probed with rabbit anti-spinach leaf GRase (Tanaka et al, 1994) diluted 1:1000, and alkaline phosphatase-conjugated goat secondary antibody to rabbit IgG, diluted 1:2500 with blocking buffer. GTase was probed with anti-Hyoscymus muticus GTase (Bilang and Sturm, 1995) diluted 1:lOOO with blocking buffer.…”

“…Synthesis of GSH is ATP-dependent and its regeneration from GSSG is catalyzed by GRase, with the consumption of NADPH (Carlberg and Mannervik, 1985). Tanaka et al (1994) suggested that GRase is responsible for the reduction of more than 90% of cellular GSSG. Furthermore, enhanced consumption of NADPH during imbibition of aged seeds may limit the availability of reducing equivalents for metabolic processes that lead directly to germination (De Vos et al, 1994).…”