Regulation of Activity and Properties of Inulinases from Roots of Cichorium Intybus L. # #This work was supported by a grant from the Indian Council of Agricultural Research, New Delhi.

Inulin is a reserve carbohydrate in the roots of Cichorium intybus L. It is hydrolysed by inulinase during flowering and seed formation. Seventy to eighty five percent of inulinase was found to be firmly bound to the cell wall. The quantity of cell wall-bound inulinase proved to be too low to be used for commercial purposes. The level of soluble inulinase in the vascular bundles was generally higher than that in the root cortex. The activity of bound inulinases of vascular bundles and cortex was characterized by a sigmoidal velocity curve with increasing inulin concentration. Sucrose was a non-competitive inhibitor of bound inulinase from vascular bundles. It may play an important role in regulating the activity of this enzyme under in vivo conditions. Metabolites like phosphoenol pyruvate, 2-phosphoglycerate, 6-phosphogluconate, and nucleotides (ADP, ATP, UDP, UTP and UDP-glucose) changed the sigmoidal pattern of inulinase activity of vascular bundles to a near-hyperbolic pattern, thus suggesting enhancement of inulinase activity at low and inhibition at high inulin concentrations. Hg 2+ was a very strong inhibitor of inulinases. The temperature optimum of bound inulinases from vascular bundles (45 °C) was higher than that of other inulinases (37 °C).