Regulation of Fructose 1,6-Bisphosphatase Activity of Chlorella by Mole Mass Change

TL;DRAbstract

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 of the large enzyme form with 5mᴍ concentrations of Mg 2+ , F1,6P 2 , DTT or ATP leads to dissociation into smaller ones of 215 -470 kDa. Aggregation/dissoziation is a reversible process, as has been shown for the effect of F1,6P 2 and of pH, by rechromatography. The change in mole 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 F1,6P 2 -treated samples. Halfsaturation constants, as well as the degree of cooperativity of the 67- and the 1350- kDa form, are different for substrate affinity, activation by Mg 2+ and DTT, and for inhibition by ATP. Both enzyme forms hydrolyse fructose 1,6 bisphosphate and seduheptulose 1,7 bisphosphate better than other phosphorylated compounds. The ratio

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