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'Water Oxidizing Enzyme' in keywords Facet   Publication Year 1995  [X]
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1Author    AchimE G Aua, HubertH. Tholeb, ElfriedeK. PistoriusaRequires cookie*
 Title    Isolation and Partial Characterization of a Manganese Requiring L-Arginine Metabolizing Enzyme Being Present in Photosystem II Complexes of Spinach and Tobacco  
 Abstract    A low L-arginine metabolizing enzyme (L -A M E) activity leading to ornithine, urea and additional products not identified so far could be detected in photosystem II (PS II) m em ­ branes of spinach and of the chlorophyll deficient tobacco mutant Su/su. The detectable L-AM E activity was very low in untreated PS II membranes, but increased significantly (about 10 fold) when the extrinsic peptides (psbO, P and Q gene products) were removed -suggesting that the L-AM E is exposed at the lumen side o f PS II. It was possible to isolate the detergent-solubilized protein from CaCl2-washed PS II membranes of spinach by a com ­ bination of anion and cation exchange columns. On the basis of SDS PAGE the protein was hom ogenous and had an apparent molecular mass of 7 kDa. N-terminal sequencing of the polypeptide gave a contiguous sequence of 20 amino acids showing no hom ologies to PS II polypeptides as yet sequenced. After chromatography o f the L-AM E on an anion exchange column at pH 9.5 (last purification step) a completely inactive enzyme was obtained. Maximal reactivation was achieved by dialyzing the protein against H epes-N aO H buffer in the pH range of 6.5 to 7.5 containing 100 m M chloride or sulfate (being the most effective anions). The L-AM E activity was totally dependent on manganese added to the reaction mixture. Moreover, there were indications of a second cation binding site being more sequestered and requiring bound Ca2+ or Mn2+ for activity (Sr2+ was less effective and Mg2+ was ineffective). There are indications that the protein contains a redox active group -possibly an amino-acid-derived quinonoid (based on a redox cycling assay with glycine and nitroblue tetrazo-lium). The capability of this PS II associated protein to bind the cofactors of water oxidation and having a redox active group (preliminary results) suggests that this protein might be functional in photosynthetic water oxidation. This is further supported by the fact that the isolated L-AM E has a low catalase activity. 
  Reference    Z. Naturforsch. 50c, 638—651 (1995); received May 22/July 10 1995 
  Published    1995 
  Keywords    L-Arginine Metabolizing Enzyme, Water Oxidizing Enzyme, Photosystem II, Quinoproteins 
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 TEI-XML for    default:Reihe_C/50/ZNC-1995-50c-0638.pdf 
 Identifier    ZNC-1995-50c-0638 
 Volume    50