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1986 (1)
1985 (1)
1Author    Remigius Manderscheid, Aloysius WildRequires cookie*
 Title    Characterization of Glutamine Synthetase of Roots, Etiolated Cotyledons and Green Leaves from Sinapis alba (L.)  
 Abstract    Glutamine synthetase of roots, etiolated cotyledons and green leaves from mustard plants cannot all clearly be separated by DEAE-Sephacel chromatography. However, the enzyme of the roots, etiolated cotyledons and green leaves, respectively, differed in the kinetic properties deter­ mined in the crude extract. The root enzyme showed a pH-optimum of about 6.9, a K m value of 3 m M for glutamate and a temperature optimum at 48 °C. Glutamine synthetase of etiolated cotyledons possessed a Km for glutamate of 6 or 12 m M , depending on the dithioerythritol con­ centration in the homogenisation buffer and a temperature optimum at 46 °C. The enzyme of green leaves was characterized by a temperature optimum at 40 °C, a pH-optimum at about 7.4 and a low glutamate affinity with positive cooperative substrate binding. Based on isolation of chloroplasts and identification of glutamine synthetase the enzyme of green leaves seems to be the chloroplastic form. This enzyme was purified by DEAE-Sephacel, hydroxylapatite and Sephacryl S-300 chromatography. Affinity for glutamate and M g S04 of the purified enzyme differed from that found in the crude extract. The function of the different isoenzymes is discussed. Intro du ction 
  Reference    Z. Naturforsch. 41c, 712 (1986); received March 17 1986 
  Published    1986 
  Keywords    Enzyme Purification, Glutamine Synthetase, Isoenzymes, Photorespiration, Sinapis alba 
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 TEI-XML for    default:Reihe_C/41/ZNC-1986-41c-0712.pdf 
 Identifier    ZNC-1986-41c-0712 
 Volume    41 
2Author    RemigiusM. Anderscheid, Aloysius WildRequires cookie*
 Title    The Effect of Thiol Compounds on the Glutamate Affinity of the Chloroplastic Glutamine Synthetase from Mustard Leaves  
 Abstract    The chloroplastic glutam ine synthetase taken from m ustard leaves shows a positive cooperative glutamate binding. The S0.5-value depends on the DTE concentration in the homogenization buffer. N orm al glutamate satura­ tion kinetics have been found with the root enzyme and the enzyme o f etiolated cotyledons. These are not influ­ enced by thiol com pounds. The possible function o f the allosteric behaviour o f GS2 is discussed. 
  Reference    Z. Naturforsch. 40c, 295 (1985); received N ovember 28 1984 
  Published    1985 
  Keywords    G lutam ine Synthetase, G lutam ate Affinity, Isoenzymes, Positive Cooperativity, Thiol Com pounds 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0295_n.pdf 
 Identifier    ZNC-1985-40c-0295_n 
 Volume    40