Partial Purification and Characterization of a Soluble $\beta$-Fructoguracosidase from Onion (Allium cepa)

A Fructan-degrading enzyme was partially purified from onion (Allium cepa)bulbs by a combination of ammonium sufate precipitation, concanavalin-A-Affinity chromatography, and ion-exchange and gel-filtration chromatography. The enzyme hydrolyzed sucrose more effectively than inulin and was identified as a $\beta$- fructofuranosidase (invertase). The optimum pH and temperature were pH 5.5 and 35$^{\circ}C$, respectively. The enzymehydrolyzed sucrose with a Km of 1.2mM . The soluble $\beta$-fructofuranosidase is likely glycoprotein based on its ability to bind the lectin concanavalin-A. The enzyme was heatlabie, with mose activity being lost at 5$0^{\circ}C$ in 1 hr of incubation. The onion $\beta$-fructofuranosidase was partially inhibited by ZnCl2 HgCl2 and CuSo4.