Sucrose-sucrose fructosyl transferase activity: A direct and rapid colorimetric procedure for the assay of plant extracts

A new method is described that allows the quantification in plant extracts of the activity of the enzyme that initiates fructan biosynthesis, sucrose-sucrose fructosyl transferase (SST, EC 2.4.1.99). The procedure is based on the use of a sucrase that does not hydrolyze the reaction product, fructosylsucrose. Thus, it allows the destruction of unreacted sucrose by converting it into monosaccharides, thus permitting the direct colorimetric estimation of fructosylsucrose. The method is faster than any of the conventional procedures, well suited for systematic and screening analysis of plant material as well as for following enzyme purification. It is also as sensitive and reproducible as a radioactive method.