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'Fructosebisphosphatase' in keywords Facet   section ZfN Section C  [X]
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1996 (1)
1993 (1)
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    N. G. Rotjohann, G. Schneider, W. KowallikRequires cookie*
 Title    Different Forms of Fructose 1,6-Bisphosphatase in Chlorella  
 Abstract    In crude extracts of Chlorella kessleri two forms of fructosebisphosphatase can be separated by ion exchange chrom atography or by acid precipitation. FBPase I is eluted from DEAE cel­ lulose at 200 m M KC1 and precipitated at pH 4.5, FBPase II is correspondingly eluted at 310 m M KC1 and soluble at pH 4.5. Both enzymes differ in substrate affinity and degree of cooperativity. Based on literature data, FBPase I is assumed to be of cytosolic and FBPase II of chloroplastic origin. The mole mass of FBPase I is identical (51-65 kDa) at pH 6.5 and pH 8.5. T hat of FBPase II is however, about four times larger at pH 6.5 (257 kDa) than at pH 8.5 (67 kDa). Other pH values have only been tried with crude cell extracts in which still larger mole masses of FBPase resulted at more acidic pH (1349 kD a at pH 6.0). The lower mole mass form of FBPase II shows three times higher catalytic activity. Reducing agents, such as DTT, also increase the activity of FBPase II in vitro. In vivo, alkalization and production o f reducing power occurs in the chloroplast stroma du­ ring illumination. If the above alterations exist in vivo, they would be a means to activate FBPase in the light. Oligomerization of FBPase II to aggregates with altered catalytic activities and kinetic prop­ erties is discussed as result of the action of specific wavelengths and to be responsible for differ­ ences in carbohydrate metabolism of Chlorella exposed to red or blue light. 
  Reference    Z. Naturforsch. 48c, 22 (1993); received October 12/November 25 1992 
  Published    1993 
  Keywords    Chlorella kessleri, Fructosebisphosphatase, Superose-FPLC, DEAE-Chrom atography, Enzyme Oligomerization 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0022.pdf 
 Identifier    ZNC-1993-48c-0022 
 Volume    48