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'Oxygen Reduction' in keywords Facet   Publication Year 1975  [X]
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1Author    ErichF. Elstner, Claus Stoffer, Adelheid HeupelRequires cookie*
 Title    Determination of Superoxide Free Radical Ion and Hydrogen Peroxide as Products of Photosynthetic Oxygen Reduction  
 Abstract    Formation of Nitrite from Hydroxylamine in the presence of illuminated chloroplast lamellae is inhibited by superoxide dismutase but not by catalase, indicating that the superoxide free radical ion and not H20 2 is responsible for the oxidation of hydroxylamine. Decarboxylation of a-keto acids on the other hand is strongly inhibited by catalase but only slightly by superoxide dismutase. Light-dependent hydroxylamine oxidation and decarboxylation of a-keto acids can be used, there­ for, as specific and sensitive probes for the determination of either the superoxide free radical ion or hydrogen peroxide, respectively. Photosynthetic oxygen reduction in the presence of ferredoxin, (monitored by the above method) yields both H20 2 and 0 2 ". The addition of an oxygen reducing factor (ORF, solubilized by heat — treatment of washed chloroplast lamellae) instead of ferredoxin, however, stimulates only the production of H20 2 , while 0 2'~ — formation is not observed. The cooperation of ferredoxin and ORF during photosynthetic oxygen reduction by chloroplast lamellae apparently produces H20 2 not only by dismutation of 0 2'~, but also by a separate mechanism involving ORF. yields only in the formation of H20 2 . The coopera­ tion of Fd and ORF in photosynthetic oxygen re­ duction provides a system which is able to produce HoOo and 0 2~ simultanuously. During photosyn­ thetic oxygen reduction, H 20 2 is not only the product of the dismutation of the superoxide free radical ion according to Eqn (1) 0 2'-+ Oo ~ + 2 H +-> H2Oo + 0 2 (1) but is separately formed by a mechanism which includes the function of ORF. Material and Methods Ferredoxin was isolated from spinach leaves9 and SOD from dried green peas 10, 5. Chloroplasts were isolated either from spinach 11 or from sugar beet leaves12' 7. ORF was prepared from isolated chloroplast lamellae 7 from either spinach or sugar beet leaves. Photosynthetic decarboxylation of [l-14C]gly-oxylate13, NADP-reduction13 and nitrite-forma-tion 14 from hydroxylamine were measured as de­ scribed. Sugar beet leaves (greenhouse cultures) were a gift from the Kleinwanzlebener Saatzucht AG, Einbeck/Hann. [1-14C] sodium glyoxylate was obtained from the Radiochemical Center, Amersham. Catalase was purchased from Boehringer, Mannheim. 
  Reference    (Z. Naturforsch. 30c, 53 [1975]; received October 25 1974) 
  Published    1975 
  Keywords    Chloroplasts, Oxygen Reduction, Hydroxylamine Oxidation, Superoxide Free Radical Ion 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0053.pdf 
 Identifier    ZNC-1975-30c-0053 
 Volume    30