Sucrases in Phaseolus vulgaris

Some properties of beta-fructofuranosidases partially purified from Phaseolus vulgaris and Solanum tuberosum

1. Soluble beta-fructofuranosidases were purified 16-fold from French-bean-pod extracts and 35-fold from potato-tuber extracts. 2. The two enzymes had similar overall properties but differed from each other quantitatively in lability and reaction kinetics. 3. A non-diffusible inhibitor of beta-fructofuranosidase was present in the potato-tuber extracts but was absent from the bean extracts. This non-competitive inhibitor was acid-labile. 4. The possible roles of imidazole, carboxyl and thiol groups in beta-fructofuranosidase action are discussed, and the properties of the bean and potato enzymes are compared with published data for yeast, mould and grape-berry enzymes.

THE DEVELOPMENT OF INVERTASE ACTIVITY IN SLICES OF THE ROOT OF BETA VULGARIS L. WASHED UNDER ASEPTIC CONDITIONS

1. When disks of root tissue from sugar or red beet (Beta vulgaris L.) are washed in running aerated tap water the sucrose contained in them disappears and glucose and fructose are formed. 2. Invertase activity in the disks has been measured by a polarimetric method. Freshly cut tissue has a very low activity, but a considerable increase occurs during the first 3-4 days of washing, the final activity being sufficient to hydrolyse the sucrose contained in the disk within a few hours. 3. Disks of red beet have been cut and shaken in water under aseptic conditions. Sucrose breakdown and invertase development still took place. Microbial contamination is therefore not responsible. 4. Trisaccharides that appear in sugar-beet disks during the washing process have been isolated and identified; their formation also suggests that a higher-plant invertase is acting. 5. The significance of these results is discussed in relation to protein synthesis in washed storage-tissue slices, and the occurrence of high invertase activity in growing plant cells.

Enzyme kinetics by mid-infrared spectroscopy: beta-fructosidase study by a one-step assay

An alternate method for enzyme study is proposed. Multidimensional statistical analysis applied on mid-infrared attenuated total reflectance spectra (Cadet et al. (1991) Appl. Spectrosc. 42, 166-172) collected during a kinetic allows a direct and fast quantification of the remaining substrate, as well as a one step enzymatic assay. Furthermore, the combination of these techniques may be used as a structural tool. The method applied to the study of beta-fructosidase is developed in this paper as an example. With appropriate calibration, the method may be extend to any enzyme.

Alkaline β-fructofuranosidases of tuberous roots: Possible physiological function

Alkaline invertase of roots of carrot (Daucus carota L.) did not hydrolyze raffinose while the acid invertase from the same tissue showed with this sugar ca. 60% of the activity found with sucrose. The activity of the two invertases was inhibited by fructose to a different extent, the K i value being ca. 4×10(-2) M and 3×10(-1)M, respectively, for the alkaline and the acid invertases from the roots of both carrot and turnip (Brassica rapa L.). It is proposed that fructose inhibition of acid invertase is of no physiological significance but that, in contrast, hexoses might regulate the activity of alkaline invertase.Comparing several species and cultivars, it was found that the content of reducing sugars and the activity of alkaline invertase of mature tuberous roots showed a positive correlation. This indicates that alkaline invertase may participate in the regulation of the hexose level of the cell, as was previously suggested for sugar-cane. A scheme is presented which proposes a way of participation of alkaline invertase in such a regulation, assuming that this enzyme is located in the cytoplasm and acid invertase is membrane-bound and mainly located at the cell surface.