Purification and Characterization of Pyrophosphate : D-Fructose 6-Phosphate 1-Phosphotransferase from Rice Seedlings

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Pyrophosphate : D-fructose 6-phosphate 1-phosphotransferase was purified to homogeneity from rice seedlings. The enzyme had an apparent molecular weight of 100,000 and consisted of a single protein. The pH optimum for the forward and reverse reactions was 8.1 and 7.9,respectively. Fructose-2,6-bisphosphate (Fru-2,6-P_2) shifted the pH optimu for both the forward and reverse reactions to slightly acidic. Half-maximum activation of the enzyme for Fru-2,6-P_2 in the forward and reverse reactions was observed at 16 and 520nM, respectively. The enzyme had normal Michaelis-Menten kinetics in both the presence and absence of Fru-2,6-P_2. Fru-2,6-P_2-stimulated the enzyme activity by increasing V_<max> for Fru-6-P and PPi, and by raising the affinity for Fru-6-P, Fru-1,6-P_2,and PPi. At a saturated concentration of Fru-2,6-P_2,Pi strongly inhibited the enzyme in the forward reaction. The Dixon plots with Pi indicated that the inhibition behavior was of the mixed type with respect to both Fru-6-P and PPi with K_i of 1.46 and 1.53 mM, respectively.
社団法人日本農芸化学会の論文
1992-02-23