Kinetic properties of an inulosucrase from Lactobacillus reuteri 121.

Inulosucrases catalyze transfer of a fructose moiety from sucrose to a water molecule (hydrolysis) or to an acceptor molecule (transferase), yielding inulin. Bacterial inulin production is rare and a biochemical analysis of inulosucrase enzymes has not been reported. Here we report biochemical characteristics of a purified recombinant inulosucrase enzyme from Lactobacillus reuteri. It displayed Michaelis-Menten type of kinetics with substrate inhibition for the hydrolysis reaction. Kinetics of the transferase reaction is best described by the Hill equation, not reported before for these enzymes. A C-terminal deletion of 100 amino acids did not appear to affect enzyme activity or product formation. This truncated form of the enzyme was used for biochemical characterization.