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1984 (2)
1Author    Ahlert SchmidtRequires cookie*
 Title    Occurrence of Mercaptopyruvate Sulfotransferase Activity in Photosynthetic Organisms  
 Abstract    Mercaptopyruvate sulfotransferase activity catalyzes the formation o f pyruvate from mercapto­ pyruvate in the presence o f suitable reagents as acceptor. It was detected in Lemna minor, Pisum sativum, Spinacia oleracea, Chlorella fusca, Synechococcus 6301, and Rhodopseudomonas palustris. Best activity was detected using dithioerythritol as a thiol reagent; good activity was obtained using mercaptoethanol, glutathione, mercaptopyruvate or sulfite as acceptor. The pH-optimum for the Chlorella mercaptopyruvate sulfotransferase was found around 9; the apparent Km for mercaptopyruvate was determined to 2 m M and for dithioerythritol for 5 m M using crude Chlorella extracts. The role of this enzyme is discussed in relation to cysteine catabolism by photosynthetic organisms. 
  Reference    Z. Naturforsch. 39c, 916—921 (1984); received April 6 1984 
  Published    1984 
  Keywords    Pyruvate, Mercaptopyruvate, Lemna, Spinacia, Pisum, Chlorella, Synechococcus, Rhodopseudomonas 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0916.pdf 
 Identifier    ZNC-1984-39c-0916 
 Volume    39 
2Author    S. G. Mauriño, M. A. Vargas, C. Echevarría, P.J A Paricio, J.M M AldonadoRequires cookie*
 Title    Red-Light Effects Sensitized by Methylene Blue on Nitrate Reductase from Spinach (Spinacia oleracea L.) Leaves  
 Abstract    Nitrate reductase from spinach (Spinacia oleracea L.) leaves, w hich had been inactivated in vitro by incubation with N A D H and cyanide, was fully reactivated in m inutes when irradiated in anaerobic conditions with red light in the presence o f m ethylene blue. Both the rate and the extent o f reactivation increased with light intensity (6 to 100 W -m " 2) and dye concentration (1 to 10 jiM). On the contrary, photoreactivation was com pletely abolished when N A D H or ethylenediaminetetra-acetic acid were present during irradiation. W e propose that m ethylene blue, when photo excited, exhibits a redox potential positive enough to reoxidise the CN~-re-duced molybdenum complex settled in the inactive enzym e, thus causing its reactivation. On the other hand, prolonged irradiation o f nitrate reductase, under air and in the presence o f methylene blue, promoted an oxygen-dependent irreversible inactivation o f the two partial activities o f the enzyme. This inactivation was m arkedly enhanced in 77% deuterated water and greatly prevented by azide, which indicates that singlet oxygen is the species primarily involved in the photooxidative inactivation o f the enzym e. 
  Reference    Z. Naturforsch. 39c, 1079—1084 (1984); received July 27 1984 
  Published    1984 
  Keywords    Methylene Blue, Nitrate Reductase, Photosensitization, Singlet O xygen, Spinacia 
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 DEBUG INFO      
 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-1079.pdf 
 Identifier    ZNC-1984-39c-1079 
 Volume    39