FTF activities and comparison of the apparent kinetic constants for FTF activity of InuJΔ144-709His inulosucrase protein of L. johnsonii at different temperatures and at sucrose concentrations of 5 to 500 mMa

ParameterValuec at temp of:
Total FTF activityb (U mg−1 of protein)365719
Transglycosylationb (U mg−1 of protein)187692
Hydrolysisb (U mg−1 of protein)17827
Transglycosylation/hydrolysis ratiob1.0525.63
k 50/m, G (mM)NDdND
k cat, G (s−1)NDND
Mean Hill factor, G, ± SEM0.47 ± 0.060.76 ± 0.06
Mean k50/m, F, ± SEM (mM)11.7 ± 1.9NTe
Mean kcat, F, ± SEM (s−1)176 ± 3.4NT
k 50/m, G − F (mM)NDND
k cat, G − F (s−1)NDND
Mean Hill factor, G − F, ± SEM0.55 ± 0.100.97 ± 0.15
  • a The kinetic constants are k50/m and kcat for (i) the formation of glucose (G; total enzyme activity), (ii) the formation of fructose (F; hydrolytic enzyme activity), and (iii) glucose minus fructose (G − F; transglycosylation enzyme activity).

  • b Activity values measured at a 500 mM sucrose concentration.

  • c Enzyme assays were done with 0.45 μg ml−1 (final concentration) enzyme.

  • d ND, kinetic parameters could not be determined because the enzyme was not saturated with sucrose, resulting in high standard errors with curve fits.

  • e NT, kinetic parameters could not be determined due to high substrate inhibition.