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'Chlorella' in keywords Facet   Publication Year 1996  [X]
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1996[X]
1Author    N. G. RotjohannRequires cookie*
 Title    Regulation of Fructose 1,6-Bisphosphatase Activity of Chlorella by Mole Mass Change  
 Abstract    Fast protein liquid chromatography on Superose 6 of partially purified FBPase II from Chlorella reveals a 1350 kDa-form at pH 6.0 and a 67 kDa-form at pH 8.5. Treatment o f the large enzyme form with 5mM concentrations of Mg2+, F1,6P2, DTT or ATP leads to dissoci­ ation into smaller ones of 2 1 5 -4 7 0 kDa. Aggregation/dissoziation is a reversible process, as has been shown for the effect of F1,6P2 and of pH, by rechromatography. The change in m ole mass results in alterations of the activitiy and of the kinetic properties of the enzyme forms, obtained. Dissociation results in a 4 -6 fold increase in activity, as can be shown for F l,6 P2-treated samples. Halfsaturation constants, as well as the degree o f cooperativity of the 67-and the 1350-kDa form, are different for substrate affinity, activation by Mg2+ and DTT, and for inhibition by ATP. Both enzyme forms hydrolyse fructose 1,6 bisphosphate and seduheptulose 1,7 bis­ phosphate better than other phosphorylated compounds. The ratio o f F1,6P2-to SDP-cleav-age is 100:58 for the small enzym e form and 100: 84 for the large one. Activation of FBPase II in the light and inactivation in the dark is discussed on the basis of different oligomeric forms of the enzyme, generated by changes in the concentration of intermediates and effectors in the chloroplast stroma, leading to dissociation or aggregation. The conclusion is drawn that oligomerization of key enzymes, resulting in enzyme forms with different activities and different kinetic properties, might provide an effective mechanism for enzyme regulation in vivo. 
  Reference    Z. Naturforsch. 51c, 639 (1996); received September 14 1995/March 7 1996 
  Published    1996 
  Keywords    Chlorella, Fructosebisphosphatase, Oligomerization Activation Kinetic Properties 
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 TEI-XML for    default:Reihe_C/51/ZNC-1996-51c-0639.pdf 
 Identifier    ZNC-1996-51c-0639 
 Volume    51 
2Author    K. Burda, G. H. SchmidRequires cookie*
 Title    On the Determination of the 5-State Distribution in the Kok Model  
 Abstract    We use the Markow chain theory to analyze the oscillation pattern of oxygen evolution during water oxidation in photosystem II under short saturating light flashes. We propose a method based on the standard least square deviation (test x 2) to determine the number of 5-states in the Kok model. As pointed out by Burda et al. (1995) this information is amongst others important for the interpretation of the role of calcium for oxygen evolution. A specific mathematical representation for a situation when the S4 state is longer living than generally assumed is introduced which requires an explicit extension of the Kok model to five states. The higher stability is modelled by introducing additional decay channels, e.g. a nonvanishing probability for the transition of S3 to the 5() state and a further transition probability for the transition from S3 to 5 4. Our analysis is extended to the case of damped oscillations of oxygen evolution caused, for example, by the lack of electron acceptor or the short life time of photosystem II particles. 
  Reference    Z. Naturforsch. 51c, 329—341 (1996); received O ctober 23/D ecem ber 5 1995 
  Published    1996 
  Keywords    0 2-Evolution, o-and ^-Analysis, Transition Probabilities, Cyanobacteria, Tobacco, Chlorella 
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 TEI-XML for    default:Reihe_C/51/ZNC-1996-51c-0329.pdf 
 Identifier    ZNC-1996-51c-0329 
 Volume    51