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2000 (1)
1980 (1)
1Author    Isabel Garcia, Blanca Cifuentes, Carlos VicenteRequires cookie*
 Title    LrUsnate-Urease Interactions: Binding Sites for the Ligand  
 Abstract    L-usnic acid inactivates urease by formation o f high molecular weight aggregates which can reached by a maximum of 880 000. L-cysteine partially reverses the inactivation by stimulating the appearance of active high molecular weight polymers. The existence of two class of binding points for L-usnic acid on the urease molecule is proposed, the first showing high affinity for the ligand, related with the loss of activity, and the second, of low affinity, related to polymerization process. 
  Reference    Z. Naturforsch. 35c, 1098—1100 (1980); received N ovember 12 1979 
  Published    1980 
  Keywords    Urease Inactivation, L-Usnic Acid, L-Cysteine, Binding Points 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-1098_n.pdf 
 Identifier    ZNC-1980-35c-1098_n 
 Volume    35 
2Author    Stylianos Tsakiris3, Panagoula Angelogianni3, KleopatraH. Schulpisb, Panagiotis Behrakis3Requires cookie*
 Title    Protective Effect of L-Cysteine and Glutathione on Rat Brain Na+,K+-ATPase Inhibition Induced by Free Radicals  
 Abstract    The aim of this study was to investigate whether the preincubation of brain homogenates with L-phenylalanine (Phe), L-cysteine (Cys) or reduced glutathione (G SH) could reverse the free radical effects on N a+,K+-ATPase activity. Two well established systems were used for the production of free radicals: 1) F e S 0 4 (84 ^i m) plus ascorbic acid (400 |o.m) and 2) F e S 0 4, ascorbic acid and H20 2 (1 mM) for 10 min at 37 °C in hom ogenates o f adult rat whole brain. Changes in brain N a+,K+-ATPase activity and total antioxidant status (TAS) were studied in the presence of each system separately, with or without Phe, Cys or GSH. TAS value reflects the amount of free radicals and the capacity of the antioxidant enzymes to limit the free radicals in the homogenate. N a+,K+-ATPase was inhibited by 35 -5 0 % and TAS value was decreased by 5 0 -6 0 % by both systems of free radical production. The enzy­ matic inhibition was completely reversed and TAS value increased by 150-180% when brain homogenates were preincubated with 0.83 mM Cys or GSH. However, this N a+,K+-ATPase inhibition was not affected by 1.80 m M Phe, which produced a 4 5 -5 0 % increase in TAS value. It is suggested that the antioxidant action of Cys and GSH may be due to the binding of free radicals to sulfhydryl groups of the m olecule, so that free radicals cannot induce N a+,K+-ATPase inhibition. Moreover, Cys and GSH could regulate towards normal values the neural excitability and metabolic energy production, which may be disturbed by free radical action on N a+,K+-ATPase. 
  Reference    Z. Naturforsch. 55c, 271—2 (2000); received October 8/Decem ber 21 1999 
  Published    2000 
  Keywords    L-Cysteine, Reduced Glutathione, L-Phenylalanine, Free Radicals, N a+, K+-ATPase 
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 TEI-XML for    default:Reihe_C/55/ZNC-2000-55c-0271.pdf 
 Identifier    ZNC-2000-55c-0271 
 Volume    55