β-Fructofuranosidase from grape berries II. Solubilization of a bound fraction

• 1.

  1. A bound fraction of grabe $\text{β-}\text{fructofuranosidase}$ (EC 3.2.1.26) was solubilized by treatment with 0.2 M borate buffer (pH 8.5), whereas several other aqueous salts were without effect.

• 2.

  2. In the system described, solubilization was influenced by boric acid concentration and pH but not by presentation time. Solubilization was essentially irreversible.

• 3.

  3. Solubilization was maximal at pH 8.5; under more alkaline conditions, enzyme inactivation occurred. The decrease in amount of bound enzyme followed an inverse trend.

• 4.

  4. Borate solubilization gave a total yield of $\text{β-}\text{fructofuranosidase}$ about 190% based on the starting material. This, together with the well-known interaction of borate with carbohydrates, suggested that a masking polysaccharide was operative in the starting material.

• 5.

  5. The solubilized and soluble enzyme were partially purified and characterized. In both cases, only unsubstituted β-fructofuranosides were hydrolyzed. The Michaelis constants for sucrose were not significantly different.

• 6.

  6. The dangers inherent in comparing the relative amounts of enzymes from different tissues were underlined by this experience.