CHARACTERIZATION OF THERMOSTABLE INVERTASE FROM WINE GRAPES

The levels of invertase activity were found to vary significantly among 14 varieties of grapes tested. The crude invertases were, however, similar in both pH and temperature optima, as well as pH and thermal stabilities. The enzymes showed a high degree of thermostability and were also stable at acidic pH and high concentration of alcohol. A significant level of invertase activity persisted in several white table wines. The optimum activity of the enzyme purified from Semillon grape was observed at about 75°C and it was stable up to 70°C. Although the enzyme was stable between the pH 2 and 8, the optimum pH for its activity was about 4. The enzyme, whose molecular weight was estimated to be 65,000 by SDS polyacrylamide slab gel electrophoresis, was found to be a glycoprotein with a total carbohydrate content of 33%. This enzyme showed activity toward sucrose and raffinose, but was inactive on the other disaccharides tested. © 1989.