Oxidative turnover of soybean root glutamine synthetase. In vitro and in vivo studies
نویسندگان
چکیده
Glutamine synthetase (GS) is the key enzyme in ammonia assimilation and catalyzes the ATP-dependent condensation of NH3 with glutamate to produce glutamine. GS in plants is an octameric enzyme. Recent work from our laboratory suggests that GS activity in plants may be regulated at the level of protein turnover (S.J. Temple, T.J. Knight, P.J. Unkefer, C. Sengupta-Gopalan [1993] Mol Gen Genet 236: 315-325; S.J. Temple, S. Kunjibettu, D. Roche, C. Sengupta-Gopalan [1996] Plant Physiol 112: 1723-1733; S.J. Temple, C. Sengupta-Gopalan [1997] In C.H. Foyer, W.P. Quick, eds, A Molecular Approach to Primary Metabolism in Higher Plants. Taylor & Francis, London, pp 155-177). Oxidative modification of GS has been implicated as the first step in the turnover of GS in bacteria. By incubating soybean (Glycine max) root extract enriched in GS in a metal-catalyzed oxidation system to produce the.OH radical, we have shown that GS is oxidized and that oxidized GS is inactive and more susceptible to degradation than nonoxidized GS. Histidine and cysteine protect GS from metal-catalyzed inactivation, indicating that oxidation modifies the GS active site and that cysteine and histidine residues are the site of modification. Similarly, ATP and particularly ATP/glutamate give the enzyme the greatest protection against oxidative inactivation. The roots of plants fed ammonium nitrate showed a 3-fold increase in the level of GS polypeptides and activity compared with plants not fed ammonium nitrate but without a corresponding increase in the GS transcript level. This would suggest either translational or posttranslational control of GS levels.
منابع مشابه
Turnover of bacterial glutamine synthetase: oxidative inactivation precedes proteolysis.
We partially purified a preparation from Escherichia coli that proteolytically degrades the enzyme glutamine synthetase [L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2]. The degradation is at least a two-step process. First, the glutamine synthetase undergoes an oxidative modification. This modification leads to loss of catalytic activity and also renders the protein susceptible to proteo...
متن کاملIn Vivo and In Vitro Studies on Neutralizing Effects of Acorus calamus and Withania somnifera root extracts against Echis carinatus venom
Neutralization effects of Acorus calamus and Withania somnifera root extracts were tested against Echis carinatus venom. Both plant extracts were effectively neutralized the various pharmacological activities induced by Echis carinatus venom. About 0.14 mg of Acorus calamus and 0.16 mg of Withania somnifera root extracts were able to completely neutralize the lethal a...
متن کاملEffect of Antioxidants, Amino Acids and Plant Growth Regulators on in vitro Propagation of Rosa centifolia
Background: Rosa centifoliais commercially propagated by asexual means but in vitro propagation ensure the production of disease free and healthy plants and browning of explants creates hurdle in their multiplication. Objectives: The aim was to reduce oxidative browning of shoots of R. centifolia in MS medium during in vitro propagation. Materials and Methods: Axillary buds of R. centifolia we...
متن کاملIn Vitro Study of the Protective Effects of Hydroalcholic Extract of Soybean against Impact of Oxidative Damage on Osteogenesis and Chondrogenesis of Mouse Limb Bud
Introduction: Oxidative stress has been implicated in the pathogenesis of various diseases affecting chondrogenesis or the function of articular cartilage. The purpose of the present study was to find the effect of soybean extract on reduction of detoriation effects of oxidativestress in embryonic chondrogenesis in vitro. Methods: In order to separate ectoderm from mesenchyme, the limb buds ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Plant physiology
دوره 119 4 شماره
صفحات -
تاریخ انتشار 1999